viewWillAppear called twice

[swt2c]

In setSelectedViewController, it seems that viewWillAppear ends up getting called twice. It is called explicitly once, but calling setContentView on the window also seems to cause it to be called.

if ([controller respondsToSelector:@selector(viewWillAppear)])
    [controller viewWillAppear];

[self.window setContentView:controllerView];

Is the explicit call needed?

[sorbits]

The explicit call is required since viewWillAppear was not a system
method prior to 10.10.

It could be updated to skip the call when on Yosemite.

On 15 Dec 2014, at 22:17, Scott Talbert wrote:

In setSelectedViewController, it seems that viewWillAppear ends up
getting called twice. It is called explicitly once, but calling
setContentView on the window also seems to cause it to be called.

if ([controller respondsToSelector:@selector(viewWillAppear)])
[controller viewWillAppear];

[self.window setContentView:controllerView];

Is the explicit call needed?

---

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#32

[swt2c]

Ah, so setContentView only causes viewWillAppear on Yosemite?

What is the preferred way to check the OSX version? NSAppKitVersionNumber?

[shpakovski]

Hi guys, how about [UIViewController instancesRespondToSelector:@selector(viewWillAppear)]?

[sorbits]

Yes, only on Yosemite, the documentation says it’s called when:

• The view is about to be added to the view hierarchy of the view
  controller
• The view controller’s window is about to become visible, such as
  coming to the front or becoming unhidden

I would go with @shpakovski suggestion of instancesRespondsToSelector:
(though sent to NSViewController) — in theory this method could exist
prior to 10.10 with different semantics, but testing against
NSAppKitVersionNumber requires optionally defining version number
constants so that it works when building with the 10.9 SDK or earlier.

On 16 Dec 2014, at 22:51, Scott Talbert wrote:

Ah, so setContentView only causes viewWillAppear on Yosemite?

What is the preferred way to check the OSX version?
NSAppKitVersionNumber?

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#32 (comment)

[swt2c]

So we'd want something like this?

    if (![NSViewController instancesRespondToSelector:@selector(viewWillAppear)])
        if ([controller respondsToSelector:@selector(viewWillAppear)])
            [controller viewWillAppear];

[shpakovski]

Yes, but it would be great to test on earlier OS X versions before shipping :) Thanks in advance for the pull request!

[sorbits]

Would also be good to add a comment about the code, as I’m sure
someone will wonder why we call a method on an object only if that
object’s superclass does not respond to said method.

On 22 Dec 2014, at 13:48, Vadim Shpakovski wrote:

Yes, but it would be great to test on earlier OS X versions before
shipping :) Thanks in advance for the pull request!

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#32 (comment)

[fingolfin]

I just tested on 10.8.5, and everything seems to work fine with the change proposed by @swt2c -- but I also agree with @sorbits that this is the kind of change that really would benefit from a short source comment explaining what it is about (and perhaps also pointing to this issue).

[shpakovski]

I believe the comment with URL to the current page would work best :)