Re: [Pyobjc-dev] Need a little direction with delegates and main event loop

[Ronald O. <ous...@ci...>]

On Monday, 21 July, 2003, at 22:25, Zachery Bir wrote:

> Hey, all.
>
> I'm about 80% of the way done with my first PyObjC app. I've based it=20=

> on Bill's Cocoa-Python Application template. I've done enough tweaking=20=

> to both the MyAppDelegate and MainMenu.nib, that I think I'm off-track=20=

> a bit. Here is some background info on the app and some particular=20
> issues I'm facing:
>
> It's a "nativication" of Casey Duncan's zopeedit.py, a client-side=20
> helper app for his External Editor product for Zope [1]. The=20
> server-side method marshalls any editor-worthy Zope object (could be=20=

> text, like Python Scripts, Zope Page Templates, DTML Methods, &c or it=20=

> could be images, like gif, jpeg, png, &c) and prepends it with several=20=

> lines of RFC822 headers of useful metadata. The client side script=20
> strips those off for use internally, writes the remaining file out to=20=

> a temp file, and launches an editor based on a lookup of the=20
> content-type/meta-type in an editor mapping. This file zopeedit.py=20
> works fine as a standalone on Linux/Windows, but it seems that Mac=20
> browsers won't accept an arbitrary file (albeit executable) as a valid=20=

> helper. This can be somewhat worked around by wrapping the python=20
> script in an AppleScript wrapper and using _that_ as the helper app,=20=

> but it doesn't work for all kinds of editors (notably Carbon apps -=20
> with Cocoa apps, I can typically point to the underlying binary in an=20=

> app bundle - can't seem to do that with Carbon apps, even if they're=20=

> bundled). So I set about writing my own app in PyObjC, so I could=20
> reuse as much code as possible, and extend it where I can to make a=20
> more pleasant UI. After cautiously (and incessantly) pestering Bill, I=20=

> was able to create an Application Delegate whose openFile_: method I=20=

> overrode to strip the file, look up the appropriate editor (using=20
> NSUserDefaults now instead of ConfigParser), and open the stripped=20
> file with it. Works great.
>
> Some issues:
>
>   =95=A0Now, unfortunately, I need to fulfill the main loop of the=20
> zopeedit script, and I'm at a bit of a loss on how to do that in the=20=

> template I'm using. Its __main__.py just jumps right into=20
> AppHelper.runEventLoop(). Coupled with the desire to have a bit more=20=

> control over the event loop, I need to set up some initial app=20
> attributes (my current workaround is ugly and doesn't seem to work=20
> terribly well anyway).

There is not much you can do about the runloop, maybe NSRunLoop has=20
methods that allow you to do the outer loop yourself (e.g. while 1:=20
someRunLoop.step()) but that is almost certainly not the right=20
solution.

If you only want to setup some global state you can do that before the=20=

call to runEventLoop. For timed events look at NSTimer, ....

>
>   =95=A0I'm trying to make a nice UI table of currently open edits =
showing=20
> filename and application editing them. I understand the need to=20
> delegate the class that will fulfill the various tableView_...=20
> methods, but I'm not sure a) where to make the connections in the nib=20=

> file, and b) where to define their implementation in the project.

There is only one connection in the NIB file for this: from the=20
TableView to its data source. The relevant outlet of NSTableView is=20
named dataSource. The TableView example shows you how to implement=20
them.

>
> Here's a rough breakdown of what I'm looking at:
>
>   =95=A0My app has a data structure of some sort holding current edits=20=

> (filename, the app that will edit them, and associated metadata used=20=

> for pushing the changes back to the server) I'd like this to be=20
> established in the creation of the app - does this belong in=20
> __main__.py? Originally, I tried establishing this in=20
> applicationDidFinishLaunching_(), but application_openFile_() is=20
> called before that, so I tried moving it to=20
> applicationWillFinishLaunching_(), and still it seems not to have been=20=

> made correctly.
IIRC applicatonWillFinishLaunching_ is called just before=20
applicationDidFinishLaunching, that won't help. I'd create the initial=20=

state before calling runEventLoop, and probably in the same file as the=20=

rest of the implementation of the model.
>
>   =95=A0This data structure needs to fulfill the NSTableDataSource =
methods=20
> to be set as the data source of the table view. Does this data=20
> structure need to be accounted for in the nib? Or just in Python code=20=

> - meaning, does it need to extend NibClassBuilder.AutoBaseClass?
See the TableView example. The datastructure itself need not be present=20=

in the NIB. I'd keep the model seperate from the controller. The=20
TableView example doesn't do this, I'll fix that.

What I find usefull is using a seperate class for storing the state,=20
and using the controller object (which is mentioned in the NIB) to=20
shuffle data to/from that state.

>
>   =95=A0The original script just runs with a while: 1 loop watching =
over=20
> the tempfile it creates and pushes the file back to the server when=20
> the mod time changes. I'd prefer to use notifications (seems more=20
> elegant), but if I can extend the main event loop with this behavior,=20=

> that would be an acceptable initial concession.

You can use timers to check if the modification time changes. I don't=20
know if there is a higher level API for this (like notification).

>
> That's basically it. It's an exceedingly simple python script, but=20
> turning it into a full Mac OS X app has proved challenging (mostly=20
> because I don't have my Cocoa experience - I'm sure all these feature=20=

> requirements are very simple to the initiated) :)

Cocoa starts out pretty simple, but most people seem to suffer from a=20
setback soon until they grasp the ideas behind Cocoa.

Ronald

>
> Thanks,
>
> Zac
>
> [1] External Editor product:=20
> <http://www.zope.org/Members/Caseman/ExternalEditor> - You don't need=20=

> Zope expertise to understand the client-side aspect.
>
>
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