Thread: [Mysql-cocoa-users] Re: SMySQL framework
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From: Serge C. <ser...@us...> - 2003-02-26 10:13:55
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Dear Lorenz Sorry not to have answered earlier. I'll try to give you as much info=20 as I can: For the SSL issue: I'm afraid I can not answer the question for sure. What I can tell you=20= is that on Jaguar (10.2.3 indeed) I managed to compile MySQL with SSL=20 support (including the libmysqlclient library onn which I rely to make=20= connection to MySQL servers). This means that even if it is not already=20= possible to use the framework as is for connecting to MySQL using SSL,=20= it should not be too difficult to get to this point. For the answer of how to manage to do it, I can suggest to ways: 1. Look the documentation of MySQL (client library) and check what is=20= required to have a SSL connection. Maybe you need to set a particular=20 flag from the MYSQL pointer. Than you can do it by default (changing=20 default in the source of the framework). 2. You can also add a method to MCPConnection to be able to set this=20= option at runtime. 3. If you can still wait a month (or maybe a bit more), you can wait=20= for me to have the time to make it. I need this time because I have a=20 lot of work now and I also need to set a SSL aware MySQL server to test=20= the new sources... which will take a bit of time for me because I've=20 never done anything similar alreasdy (basically the time to read doc,=20 reset properly the setting of my testing server, and then ONLY I can=20 modify the MCPConnection...). By the way, if you chose sol. 2. I'm (obviously) interested by the=20 modification you make to MCPConnection for further inclusion in the=20 framework (more likely as the basis of new addition to the framework). For the table type: I don't have precise answer here neither... BUT I have InnoDB running=20 on my mac, and event if so far I've never used through the framework,=20 it should not be to hard for me to test it. SO I'll try to give you a=20 documented answer in the coming two weeks (still I don't foresee any=20 reasons for that 'incompatibility', ie. my guess would be that the=20 problem does not come from the framework). For the last question I'm not sure to get it right. Let me try to=20 rephrase it (and tell if I'm wrong): When you retrieve a BLOB (or TEXT) from the DB it comes as a NSData=20 object. You want this NSData object to be (eventualy) edited as text by=20= the user. The problem you are facing is that if you transform this=20 NSData to a NSString and convert it back to a NSData later the two=20 NSData are different (so if your NSData correspond to a binary format,=20= the data gets corrupted). If this is the problem you are facing... I'll have a look to see what=20 can we do about it. The main problem I'm facing with TEXT and BLOB=20 column in a table is that one can not discriminate between the two (or=20= at least I don't know how to do it) without issuing a 'DESCRIBE'=20 command on the table (they give the same type in the MYSQL_RES field=20 types). Indeed after seeing the framework again I think the normal solution=20 would be not to use prepareBinaryData: but prepareString: instead. ie=20 once your NSData has been transformed into a string (By the way you can=20= use the method stringWithText: for that), you don't want to use=20 prepareBinaryData on it anymore. Sorry for not answering your question (still I hope you get some=20 clues), thank you very much for your feed back, and I'd hope we will=20 continue this thread whenever we have time (meaning: sorry in advance=20 if I take some time to answer to your next mail). Serge. PS: As you see, I posted this also to the user mailing list. Please I'd=20= like that all these mails go there instead of directly to me. I AM=20 READING the list, and I'm not the only one (from the number of people=20 inscribed there). I'm sure some of the few persons there might have=20 already experienced some of your problems and can help you (and me at=20 the same time). PPS: I'd be interested to know which version of the framework you are=20 using, and on what version of your own software you already are. PPPS: last remark: If the problem is the very (very) low traffic on the=20= mailing list, just consider that the traffic has to start on some=20 time... PPPPS: Sorry one more: remind me of linking to your project from the=20 framework page if it is not already done. Le mercredi, 19 f=E9v 2003, =E0 10:13 Europe/Amsterdam, Lorenz Textor a=20= =E9crit : > Hi Serge, > > As I wrote to you some months ago I'm developing an application called=20= > CocoaMySQL using your framework to connect to the MySQL server (see=20 > cocoamysql.sourceforge.net). Thanks again for coding this great=20 > framework and for making it open-source! > > I have some questions regarding the framework: > - Many persons asked me if it is possible to connect securely to the=20= > MySQL server using SSL. I looked a bit at the MySQL C API and think=20 > there is an option to do it. Would it be difficult to change the=20 > framework so that secure connections are possible? Or is it possible=20= > with the current version yet? > - Some people wrote me they have problems using other table types=20 > (InnoDB for example). Can this be a problem of the framework? > - How can I represent a BLOB field (NSData object) as a string that=20 > can be edited and saved to the database afterwards? I don't want the=20= > string to be escaped, so I can use prepareBinaryData: only after=20 > editing. Now I'm using something like > [[NSString alloc] initWithData:theData encoding:[mySQLConnection=20= > encoding]]; > In most cases this works, but with binary data (for example images)=20 > the data gets corrupted. > > Thank you for your help! > Best Regards, > Lorenz > > > ---------------------------------------------------- Serge Cohen GPG Key ID: Non-Available for the moment. ---------------------------------------------------- |
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From: Lorenz T. <lo...@te...> - 2003-03-08 15:52:01
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P.S. I have searched a bit in this mail list and I think that I will=20 make it like this (regarding the problem of editing fields containing=20 binary data): - test if field is blob or text (using a DESCRIBE syntax if I don't=20 find another way) - use the method stringWithText: if it is a text field - if it is a blob field: maybe I will use the method prepareBinaryData:=20= (the only problem is that then the string is escaped which isn't so for=20= all other field types in my app) Thanks again for your help, Lorenz On Wednesday, February 26, 2003, at 12:14 AM, Serge Cohen wrote: > Dear Lorenz > > Sorry not to have answered earlier. I'll try to give you as much info=20= > as I can: > > For the SSL issue: > I'm afraid I can not answer the question for sure. What I can tell you=20= > is that on Jaguar (10.2.3 indeed) I managed to compile MySQL with SSL=20= > support (including the libmysqlclient library onn which I rely to make=20= > connection to MySQL servers). This means that even if it is not=20 > already possible to use the framework as is for connecting to MySQL=20 > using SSL, it should not be too difficult to get to this point. > For the answer of how to manage to do it, I can suggest to ways: > 1. Look the documentation of MySQL (client library) and check what is=20= > required to have a SSL connection. Maybe you need to set a particular=20= > flag from the MYSQL pointer. Than you can do it by default (changing=20= > default in the source of the framework). > 2. You can also add a method to MCPConnection to be able to set this=20= > option at runtime. > 3. If you can still wait a month (or maybe a bit more), you can wait=20= > for me to have the time to make it. I need this time because I have a=20= > lot of work now and I also need to set a SSL aware MySQL server to=20 > test the new sources... which will take a bit of time for me because=20= > I've never done anything similar alreasdy (basically the time to read=20= > doc, reset properly the setting of my testing server, and then ONLY I=20= > can modify the MCPConnection...). > > By the way, if you chose sol. 2. I'm (obviously) interested by the=20 > modification you make to MCPConnection for further inclusion in the=20 > framework (more likely as the basis of new addition to the framework). > > > > For the table type: > I don't have precise answer here neither... BUT I have InnoDB running=20= > on my mac, and event if so far I've never used through the framework,=20= > it should not be to hard for me to test it. SO I'll try to give you a=20= > documented answer in the coming two weeks (still I don't foresee any=20= > reasons for that 'incompatibility', ie. my guess would be that the=20 > problem does not come from the framework). > > > > For the last question I'm not sure to get it right. Let me try to=20 > rephrase it (and tell if I'm wrong): > When you retrieve a BLOB (or TEXT) from the DB it comes as a NSData=20 > object. You want this NSData object to be (eventualy) edited as text=20= > by the user. The problem you are facing is that if you transform this=20= > NSData to a NSString and convert it back to a NSData later the two=20 > NSData are different (so if your NSData correspond to a binary format,=20= > the data gets corrupted). > > If this is the problem you are facing... I'll have a look to see what=20= > can we do about it. The main problem I'm facing with TEXT and BLOB=20 > column in a table is that one can not discriminate between the two (or=20= > at least I don't know how to do it) without issuing a 'DESCRIBE'=20 > command on the table (they give the same type in the MYSQL_RES field=20= > types). > Indeed after seeing the framework again I think the normal solution=20 > would be not to use prepareBinaryData: but prepareString: instead. ie=20= > once your NSData has been transformed into a string (By the way you=20 > can use the method stringWithText: for that), you don't want to use=20 > prepareBinaryData on it anymore. > > Sorry for not answering your question (still I hope you get some=20 > clues), thank you very much for your feed back, and I'd hope we will=20= > continue this thread whenever we have time (meaning: sorry in advance=20= > if I take some time to answer to your next mail). > > Serge. > > PS: As you see, I posted this also to the user mailing list. Please=20 > I'd like that all these mails go there instead of directly to me. I AM=20= > READING the list, and I'm not the only one (from the number of people=20= > inscribed there). I'm sure some of the few persons there might have=20 > already experienced some of your problems and can help you (and me at=20= > the same time). > > PPS: I'd be interested to know which version of the framework you are=20= > using, and on what version of your own software you already are. > > PPPS: last remark: If the problem is the very (very) low traffic on=20 > the mailing list, just consider that the traffic has to start on some=20= > time... > > > PPPPS: Sorry one more: remind me of linking to your project from the=20= > framework page if it is not already done. > > > Le mercredi, 19 f=E9v 2003, =E0 10:13 Europe/Amsterdam, Lorenz Textor = a=20 > =E9crit : > >> Hi Serge, >> >> As I wrote to you some months ago I'm developing an application=20 >> called CocoaMySQL using your framework to connect to the MySQL server=20= >> (see cocoamysql.sourceforge.net). Thanks again for coding this great=20= >> framework and for making it open-source! >> >> I have some questions regarding the framework: >> - Many persons asked me if it is possible to connect securely to the=20= >> MySQL server using SSL. I looked a bit at the MySQL C API and think=20= >> there is an option to do it. Would it be difficult to change the=20 >> framework so that secure connections are possible? Or is it possible=20= >> with the current version yet? >> - Some people wrote me they have problems using other table types=20 >> (InnoDB for example). Can this be a problem of the framework? >> - How can I represent a BLOB field (NSData object) as a string that=20= >> can be edited and saved to the database afterwards? I don't want the=20= >> string to be escaped, so I can use prepareBinaryData: only after=20 >> editing. Now I'm using something like >> [[NSString alloc] initWithData:theData encoding:[mySQLConnection=20= >> encoding]]; >> In most cases this works, but with binary data (for example images)=20= >> the data gets corrupted. >> >> Thank you for your help! >> Best Regards, >> Lorenz >> >> >> > ---------------------------------------------------- > Serge Cohen > > GPG Key ID: Non-Available for the moment. > ---------------------------------------------------- > > --=20 lorenz textor ** sh ** eigerstrasse 21 8200 schaffhausen tf 052 - 624 27 91 ** ticino ** via delle scuole 41 6963 pregassona tf 091 - 940 20 57 ** mobile 076 - 531 71 74 email lo...@te... |
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From: Lorenz T. <lo...@te...> - 2003-03-08 15:24:45
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Dear Serge, Thank you very much for taking the time to respond so detailed. > Sorry not to have answered earlier. I'll try to give you as much info=20= > as I can: As you see I had much longer to answer (I was in holidays and hadn't=20 the possibility to check my emails ;-) > For the SSL issue: > I'm afraid I can not answer the question for sure. What I can tell you=20= > is that on Jaguar (10.2.3 indeed) I managed to compile MySQL with SSL=20= > support (including the libmysqlclient library onn which I rely to make=20= > connection to MySQL servers). This means that even if it is not=20 > already possible to use the framework as is for connecting to MySQL=20 > using SSL, it should not be too difficult to get to this point. > For the answer of how to manage to do it, I can suggest to ways: > 1. Look the documentation of MySQL (client library) and check what is=20= > required to have a SSL connection. Maybe you need to set a particular=20= > flag from the MYSQL pointer. Than you can do it by default (changing=20= > default in the source of the framework). I found in the documentation that I can set the flag CLIENT_SSL in the=20= mysql_real_connect() function. By now I have no possibility to test it=20= because I have not set up my system to work with SSL. If I will find=20 the time, I'll try to set up a test server and test it with your=20 framework. > 2. You can also add a method to MCPConnection to be able to set this=20= > option at runtime. I would make it like this, because the standard way to connect would=20 remain without SSL. > 3. If you can still wait a month (or maybe a bit more), you can wait=20= > for me to have the time to make it. I need this time because I have a=20= > lot of work now and I also need to set a SSL aware MySQL server to=20 > test the new sources... which will take a bit of time for me because=20= > I've never done anything similar alreasdy (basically the time to read=20= > doc, reset properly the setting of my testing server, and then ONLY I=20= > can modify the MCPConnection...). > > By the way, if you chose sol. 2. I'm (obviously) interested by the=20 > modification you make to MCPConnection for further inclusion in the=20 > framework (more likely as the basis of new addition to the framework). I would be glad to help you with this modifications, but unfortunately=20= I also haven't a lot of time to work on these things (and it would take=20= me a lot of time to set up SSL because I never worked with it, and I am=20= rather a Unix newbie too...). > > For the table type: > I don't have precise answer here neither... BUT I have InnoDB running=20= > on my mac, and event if so far I've never used through the framework,=20= > it should not be to hard for me to test it. SO I'll try to give you a=20= > documented answer in the coming two weeks (still I don't foresee any=20= > reasons for that 'incompatibility', ie. my guess would be that the=20 > problem does not come from the framework). I'm nearly sure that this is a problem of the MySQL server=20 configuration. But I never worked with this tables and therefore I=20 can't be sure of this. If you could try it (maybe with my app), it=20 would be great, but it isn't that important or urgent. > For the last question I'm not sure to get it right. Let me try to=20 > rephrase it (and tell if I'm wrong): > When you retrieve a BLOB (or TEXT) from the DB it comes as a NSData=20 > object. You want this NSData object to be (eventualy) edited as text=20= > by the user. The problem you are facing is that if you transform this=20= > NSData to a NSString and convert it back to a NSData later the two=20 > NSData are different (so if your NSData correspond to a binary format,=20= > the data gets corrupted). It is exactly like this. The string I get from the NSData is for=20 example like this: GIF89a=03=01 plus a lot of strange characters After writing it to the db, there is only the GIF89a=03=01 without the = rest=20 of the string (although I escaped the string using the method=20 prepareString:). I think the method I use to extract the string=20 ([[NSString alloc] initWithData:theValue encoding:[mySQLConnection=20 encoding]]) is wrong. Maybe the problem is that the string contains characters which=20 "terminate" the string, for example if I insert the string in a text=20 file, I don't see anymore the cursor or the end of the file. The same=20 thing happens with the dump files my app writes; there I use the method=20= prepareBinaryData: with the original NSData objects. Reading the dump=20 afterwards works fine, but when I open the file using TextEdit, it=20 displays only the beginning of the file. > > If this is the problem you are facing... I'll have a look to see what=20= > can we do about it. The main problem I'm facing with TEXT and BLOB=20 > column in a table is that one can not discriminate between the two (or=20= > at least I don't know how to do it) without issuing a 'DESCRIBE'=20 > command on the table (they give the same type in the MYSQL_RES field=20= > types). > Indeed after seeing the framework again I think the normal solution=20 > would be not to use prepareBinaryData: but prepareString: instead. ie=20= > once your NSData has been transformed into a string (By the way you=20 > can use the method stringWithText: for that), you don't want to use=20 > prepareBinaryData on it anymore. I'm using the method prepareString:, but it doesn't work. What is the=20 method stringWithText:? I haven't found it in the documentation. Anyway, this isn't very important because it works well with "normal"=20 (non binary) blob fields and some binary blob fields too; and it=20 doesn't make much sense to edit a binary data as a string. Dumping the=20= table or editing a row containing this blob fields works well too. > > Sorry for not answering your question (still I hope you get some=20 > clues), thank you very much for your feed back, and I'd hope we will=20= > continue this thread whenever we have time (meaning: sorry in advance=20= > if I take some time to answer to your next mail). Thank you for helping me and for developing the framework! I would be=20 glad to continue this thread too, but I will also need a bit of time to=20= answer ;-) > Serge. > > PS: As you see, I posted this also to the user mailing list. Please=20 > I'd like that all these mails go there instead of directly to me. I AM=20= > READING the list, and I'm not the only one (from the number of people=20= > inscribed there). I'm sure some of the few persons there might have=20 > already experienced some of your problems and can help you (and me at=20= > the same time). I will make it like this starting with this email! > PPS: I'd be interested to know which version of the framework you are=20= > using, and on what version of your own software you already are. The version I use is still the beta of the version 1.0. I would like to=20= update to v2.0, but I haven't found the time to make the necessary=20 changes to my code (especially I would have to test the app very=20 carefully to be sure that all things work like they worked before).=20 Anyway, all the methods I use in my app work perfectly! The current version of my CocoaMySQL is v0.4 (which I will release=20 after some final testing this evening or tomorrow). You find it on=20 cocoamysql.sourceforge.net if you are interested... > PPPS: last remark: If the problem is the very (very) low traffic on=20 > the mailing list, just consider that the traffic has to start on some=20= > time... That's right. I have subscribed to it today and will try to contribute=20= to the list as much as I can! > > PPPPS: Sorry one more: remind me of linking to your project from the=20= > framework page if it is not already done. This would be great! I have placed a link to the framework page=20 (http://mysql-cocoa.sourceforge.net/) on my site (hope this is the=20 right page). Best Regards, Lorenz > > Le mercredi, 19 f=E9v 2003, =E0 10:13 Europe/Amsterdam, Lorenz Textor = a=20 > =E9crit : > >> Hi Serge, >> >> As I wrote to you some months ago I'm developing an application=20 >> called CocoaMySQL using your framework to connect to the MySQL server=20= >> (see cocoamysql.sourceforge.net). Thanks again for coding this great=20= >> framework and for making it open-source! >> >> I have some questions regarding the framework: >> - Many persons asked me if it is possible to connect securely to the=20= >> MySQL server using SSL. I looked a bit at the MySQL C API and think=20= >> there is an option to do it. Would it be difficult to change the=20 >> framework so that secure connections are possible? Or is it possible=20= >> with the current version yet? >> - Some people wrote me they have problems using other table types=20 >> (InnoDB for example). Can this be a problem of the framework? >> - How can I represent a BLOB field (NSData object) as a string that=20= >> can be edited and saved to the database afterwards? I don't want the=20= >> string to be escaped, so I can use prepareBinaryData: only after=20 >> editing. Now I'm using something like >> [[NSString alloc] initWithData:theData encoding:[mySQLConnection=20= >> encoding]]; >> In most cases this works, but with binary data (for example images)=20= >> the data gets corrupted. >> >> Thank you for your help! >> Best Regards, >> Lorenz >> >> >> > ---------------------------------------------------- > Serge Cohen > > GPG Key ID: Non-Available for the moment. > ---------------------------------------------------- > > --=20 lorenz textor ** sh ** eigerstrasse 21 8200 schaffhausen tf 052 - 624 27 91 ** ticino ** via delle scuole 41 6963 pregassona tf 091 - 940 20 57 ** mobile 076 - 531 71 74 email lo...@te... |
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From: John G. <jo...@jl...> - 2003-03-10 21:54:56
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> Hi Lorenz, I've been using the Framwork for a while, and I have used BLOBs a=20 little bit so I can offer you some overviews that may help you. Over the last year I have used BLOBS in two ways, first I have embedded=20= word documents in a BLOB, and retrieved them using a cgi application I=20= wrote in Cocoa, everything worked properly. Secondly I have used a BLOB=20= to contain a LONGTEXT as in the older version of the Framework I am=20 using it couldn't support large text columns. comments below: >> For the last question I'm not sure to get it right. Let me try to=20 >> rephrase it (and tell if I'm wrong): >> When you retrieve a BLOB (or TEXT) from the DB it comes as a NSData=20= >> object. You want this NSData object to be (eventualy) edited as text=20= >> by the user. The problem you are facing is that if you transform this=20= >> NSData to a NSString and convert it back to a NSData later the two=20 >> NSData are different (so if your NSData correspond to a binary=20 >> format, the data gets corrupted). > It is exactly like this. The string I get from the NSData is for=20 > example like this: > GIF89a=03=01 plus a lot of strange characters > After writing it to the db, there is only the GIF89a=03=01 without the=20= > rest of the string (although I escaped the string using the method=20 > prepareString:). I think the method I use to extract the string=20 > ([[NSString alloc] initWithData:theValue encoding:[mySQLConnection=20 > encoding]]) is wrong. > Maybe the problem is that the string contains characters which=20 > "terminate" the string, for example if I insert the string in a text=20= > file, I don't see anymore the cursor or the end of the file. The same=20= > thing happens with the dump files my app writes; there I use the=20 > method prepareBinaryData: with the original NSData objects. Reading=20 > the dump afterwards works fine, but when I open the file using=20 > TextEdit, it displays only the beginning of the file. > Basically a BLOB gives you an NSData object (Binary data basically) if=20= at any point you convert this to some form of string, unless it is=20 escaped somehow you will lose some part of the binary data and=20 therefore can't get back the original. When I was putting Binary data (word docs) INTO the database I had to=20 use prepareBinaryData to escape the data in my NSData object so I could=20= include it in the SQL INSERT statement. However when I retrieved the=20 data from the database it came out as an NSData object and needed no=20 further modification. When I was storing Long Text data in the BLOB, I did not need to modify=20= my source data when inserting it into the DB (I do actually=20 prepareStringData since it is user supplied and if they include certain=20= characters it corrupts the SQL), however when I retrieve the data from=20= the database I need to convert my NSData object back to an NSString=20 object using a suitable dataEncoding. >> >> If this is the problem you are facing... I'll have a look to see what=20= >> can we do about it. The main problem I'm facing with TEXT and BLOB=20 >> column in a table is that one can not discriminate between the two=20 >> (or at least I don't know how to do it) without issuing a 'DESCRIBE'=20= >> command on the table (they give the same type in the MYSQL_RES field=20= >> types). >> Indeed after seeing the framework again I think the normal solution=20= >> would be not to use prepareBinaryData: but prepareString: instead. ie=20= >> once your NSData has been transformed into a string (By the way you=20= >> can use the method stringWithText: for that), you don't want to use=20= >> prepareBinaryData on it anymore. > I'm using the method prepareString:, but it doesn't work. What is the=20= > method stringWithText:? I haven't found it in the documentation. > > Anyway, this isn't very important because it works well with "normal"=20= > (non binary) blob fields and some binary blob fields too; and it=20 > doesn't make much sense to edit a binary data as a string. Dumping the=20= > table or editing a row containing this blob fields works well too. > my understanding is prepareBinaryData does the SQL text encoding to=20 represent binary data in an SQL string (it applies all sorts of escape=20= sequences) prepareStringData escapes the information in the string so that it is=20 safe to include in an SQL statement, for example it escapes characters=20= like ' " / etc. going back to your problem, if you are writing a program that needs to=20= make sense of what is returned by SQL statements, you need some "local=20= knowledge" of what to expect. If you are building an application like I=20= am, I control what is in the DB, and therefore what i get out. If on=20 the other hand you are building a generic appilcation, like I think you=20= are with Cocoa-mysql, then you should use DESCRIBE to extract you local=20= knowledge (and cache it of course) anyway, hope some of my experience helps out JOhn |
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From: Lorenz T. <lo...@te...> - 2003-03-16 22:39:25
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Hi John, Thank you very much for helping me with my problem. It makes developing=20= of open-source applications possible! comments below: On Monday, March 10, 2003, at 10:55 PM, John Guy wrote: >> > Hi Lorenz, > > I've been using the Framwork for a while, and I have used BLOBs a=20 > little bit so I can offer you some overviews that may help you. > > Over the last year I have used BLOBS in two ways, first I have=20 > embedded word documents in a BLOB, and retrieved them using a cgi=20 > application I wrote in Cocoa, everything worked properly. Secondly I=20= > have used a BLOB to contain a LONGTEXT as in the older version of the=20= > Framework I am using it couldn't support large text columns. > > comments below: > > >>> For the last question I'm not sure to get it right. Let me try to=20 >>> rephrase it (and tell if I'm wrong): >>> When you retrieve a BLOB (or TEXT) from the DB it comes as a NSData=20= >>> object. You want this NSData object to be (eventualy) edited as text=20= >>> by the user. The problem you are facing is that if you transform=20 >>> this NSData to a NSString and convert it back to a NSData later the=20= >>> two NSData are different (so if your NSData correspond to a binary=20= >>> format, the data gets corrupted). >> It is exactly like this. The string I get from the NSData is for=20 >> example like this: >> GIF89a=03=01 plus a lot of strange characters >> After writing it to the db, there is only the GIF89a=03=01 without = the=20 >> rest of the string (although I escaped the string using the method=20 >> prepareString:). I think the method I use to extract the string=20 >> ([[NSString alloc] initWithData:theValue encoding:[mySQLConnection=20 >> encoding]]) is wrong. >> Maybe the problem is that the string contains characters which=20 >> "terminate" the string, for example if I insert the string in a text=20= >> file, I don't see anymore the cursor or the end of the file. The same=20= >> thing happens with the dump files my app writes; there I use the=20 >> method prepareBinaryData: with the original NSData objects. Reading=20= >> the dump afterwards works fine, but when I open the file using=20 >> TextEdit, it displays only the beginning of the file. >> > > Basically a BLOB gives you an NSData object (Binary data basically) if=20= > at any point you convert this to some form of string, unless it is=20 > escaped somehow you will lose some part of the binary data and=20 > therefore can't get back the original. In the meantime I understand that it doesn't make much sense to=20 represent binary data as a string (as long as it is not escaped for=20 using in MySQL queries). > When I was putting Binary data (word docs) INTO the database I had to=20= > use prepareBinaryData to escape the data in my NSData object so I=20 > could include it in the SQL INSERT statement. However when I retrieved=20= > the data from the database it came out as an NSData object and needed=20= > no further modification. Writing the data returned by the framework as a NSData object back to=20 the database works fine when using the method prepareBinaryData:. > When I was storing Long Text data in the BLOB, I did not need to=20 > modify my source data when inserting it into the DB (I do actually=20 > prepareStringData since it is user supplied and if they include=20 > certain characters it corrupts the SQL), however when I retrieve the=20= > data from the database I need to convert my NSData object back to an=20= > NSString object using a suitable dataEncoding. I do it exactly like this. It works fine when inserting "normal"=20 strings and I can display every type of binary data too (using the=20 NSString method initWithData:encoding:). Only certain binary data get=20 corrupted when trying to write it back to the database. But as written=20= above it works always fine when using the method prepareBinaryData: to=20= get the string out of the NSData object. > >>> >>> If this is the problem you are facing... I'll have a look to see=20 >>> what can we do about it. The main problem I'm facing with TEXT and=20= >>> BLOB column in a table is that one can not discriminate between the=20= >>> two (or at least I don't know how to do it) without issuing a=20 >>> 'DESCRIBE' command on the table (they give the same type in the=20 >>> MYSQL_RES field types). >>> Indeed after seeing the framework again I think the normal solution=20= >>> would be not to use prepareBinaryData: but prepareString: instead.=20= >>> ie once your NSData has been transformed into a string (By the way=20= >>> you can use the method stringWithText: for that), you don't want to=20= >>> use prepareBinaryData on it anymore. >> I'm using the method prepareString:, but it doesn't work. What is the=20= >> method stringWithText:? I haven't found it in the documentation. >> >> Anyway, this isn't very important because it works well with "normal"=20= >> (non binary) blob fields and some binary blob fields too; and it=20 >> doesn't make much sense to edit a binary data as a string. Dumping=20 >> the table or editing a row containing this blob fields works well >> = too. >> > > my understanding is prepareBinaryData does the SQL text encoding to=20 > represent binary data in an SQL string (it applies all sorts of escape=20= > sequences) > > prepareStringData escapes the information in the string so that it is=20= > safe to include in an SQL statement, for example it escapes characters=20= > like ' " / etc. > going back to your problem, if you are writing a program that needs to=20= > make sense of what is returned by SQL statements, you need some "local=20= > knowledge" of what to expect. If you are building an application like=20= > I am, I control what is in the DB, and therefore what i get out. If on=20= > the other hand you are building a generic appilcation, like I think=20 > you are with Cocoa-mysql, then you should use DESCRIBE to extract you=20= > local knowledge (and cache it of course) It is a generic application and I don't really know what type of data=20 is stored in the blob field (binary data such as images or only text).=20= So I will make it like you have written: Check if the field is of type=20= blob (using a DESCRIBE command), and if it is a blob using the method=20 prepareBinaryData: to get an escaped string which I can edit and write=20= back to the database. Thanks again for your help. I know now how to get this thing working in=20= the next version. Best Regards, Lorenz --=20 lorenz textor ** sh ** eigerstrasse 21 8200 schaffhausen tf 052 - 624 27 91 ** ticino ** via delle scuole 41 6963 pregassona tf 091 - 940 20 57 ** mobile 076 - 531 71 74 email lo...@te... |
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