Accessing shared instance in target application, or sending actions

[Dan Wood]

Hi folks, just trying out JSTalk for the first time since seeing Gus's
talk at C4.

I'm trying to create a new document in my target app with a minimum of
code changes in the app. I'm thinking about a couple of possible
approaches:

* [[NSDocumentController sharedDocumentController]
newDocument:nil] ... Well, the problem is that this addresses the
shared document controller for JSTalk editor, so I end up creating a
new JSTalk window!

* Could I send an action to the first responder? Not sure if it's even
possible to refer to a selector in JSTalk. If I could, I could use -
[NSApplication sendAction:to:from:]

* I guess worse-come-to-worse I could make an accessor in my
NSApplication subclass to give me the application's shared document
controller. That doesn't seem like the cleanest solution.

Thoughts?

[Gus Mueller]

On Jun 18, 2010, at 4:39 PM, Dan Wood wrote:

> * I guess worse-come-to-worse I could make an accessor in my
> NSApplication subclass to give me the application's shared document
> controller. That doesn't seem like the cleanest solution.

This is actually what I do in my apps. If you've got the JSTalk framework bundled in your app, it includes a category on NSApplication that looks like this:

- (id) sharedDocumentController {
return [NSDocumentController sharedDocumentController];
}

There's a couple more in there, which you can see in JSTExtras.m.

-gus

--

August 'Gus' Mueller
Flying Meat Inc.
http://flyingmeat.com/

[Patrick Geiller]

* [[NSDocumentController sharedDocumentController]
newDocument:nil] ... Well, the problem is that this addresses the
shared document controller for JSTalk editor, so I end up creating a
new JSTalk window!

You need to get the distant app's NSDocumentController for this to work. Distant objects don't work with classes - they do send back the class, but serve it in JSTalk's space, producing your bug : creating documents in JSTalk rather than in your app. There's a simple fix : box the distant class in a custom object, call your class methods (sharedDocumentController) on this distant object, and let this distant object forward calls to the distant class.

This will require a box class, some additions to your app's NSApplication, and will let you use distant classes like this : 

var sketch = JSTalk.application_("Sketch");

// Get distant NSDocumentController class

[[[sketch NSDocumentController] sharedDocumentController] newDocument:nil]

// Same, but using a standard method call

[[[sketch classNamed:'NSDocumentController'] sharedDocumentController] newDocument:nil]

First, this object boxes a class and forwards its calls to it :

@implementation ClassBox

+ (id)withClass:(Class)c

{

id o = [[self new] autorelease];

[o setValue:c forKey:@"class"];

return o;

}

// Check boxed class for selector response

- (BOOL)respondsToSelector:(SEL)sel

{

BOOL b = [super respondsToSelector:sel];

if (!b)

b = [class respondsToSelector:sel];

return b;

}

// Query boxed class for method signature

- (NSMethodSignature *)methodSignatureForSelector:(SEL)sel

{

id sig = [super methodSignatureForSelector:sel];

if (!sig)

{

Method m = class_getClassMethod(class, sel);

if (!m) return nil;

sig = [NSMethodSignature signatureWithObjCTypes:method_getTypeEncoding(m)];

}

return sig;

}

// Invoke boxed class

- (void)forwardInvocation:(NSInvocation *)invocation

{

[invocation setTarget:class];

[invocation invoke];

}

@end

Then, add these methods to NSApplication to get any distant class (boxed). The first method is enough to work by using [sketch classNamed:'....']. The last three treat an unknown selector as a class request and send the class back (boxed) if they find it, letting you call [sketch NSDocumentController]. 

@implementation NSApplication (ServeClassesToDistantObjects)

// [sketch classNamed:@"NSDocumentController"]

- (id)classNamed:(NSString*)name

{

id class = objc_getClass([name UTF8String]);

if (!class) return nil;

return [ClassBox withClass:class];

}

// The next three methods handle getting a distant class by using its name as selector, eg [sketch NSDocumentController]

// These might need to be swizzled

- (BOOL)respondsToSelector:(SEL)sel

{

BOOL b = [super respondsToSelector:sel];

if (!b)

{

if (objc_getClass([NSStringFromSelector(sel) UTF8String]))

return YES;

}

return b;

}

- (NSMethodSignature *)methodSignatureForSelector:(SEL)sel

{

id sig = [super methodSignatureForSelector:sel];

if (!sig)

{

// We're calling a method that doesn't exist, takes no parameters, and returns an object (the class)

// use the signature of -(id)self which does the same thing

if (objc_getClass([NSStringFromSelector(sel) UTF8String]))

return [NSMethodSignature signatureWithObjCTypes:method_getTypeEncoding(class_getInstanceMethod([self class], @selector(self)))];

}

return sig;

}

- (void)forwardInvocation:(NSInvocation *)invocation

{

id class = [self classNamed:NSStringFromSelector([invocation selector])];

[invocation setReturnValue:&class];

}

@end

You might need to swizzle the last three methods as they could interfere with NSApplication's implementations (if they exist).

-Patrick