Is there a function for "processing messages", i.e. updating screen, responding to accumulated user input

I have encountered a strange 开发者_JAVA百科bug in my application, and I am trying to debug it using step execution.

However it seems that things on an iphone often do not happen as synchronously as I would like, for example when I step-over this line [self.view addSubview:FinndomoEmbeddedMWView.view]; nothing happens in the emulator. If I just let the program run, the view is added and the screen changes as it should.

So I am guessing, addSubview does not do everything related to adding a view, it just sort of starts the process, and then it is completed later.

I don't know if there are message queues on ios similair to winapi, but there must be something like that, so is there a function for "processing all accumulated messages". I would then like to call this function after my addSubview and actually see the things change in the emulator while I debug, not when the program is running.

And I experience this not only with addSubview, so I want to have a general solution for things like this.

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Sat yesterday and found out the answer:

NSDate *dtr = [[NSDate alloc] initWithTimeIntervalSinceNow:0.5];
[[NSRunLoop currentRunLoop] runMode:NSDefaultRunLoopMode beforeDate:dtr];

This is sort of what I wanted. As you can see, this particular code may end up waiting for 0.5 seconds if there are no more events, and if there are events pending, it is only processing the first one and then returns (according to documentation).

But that could be avoided of course, this is just an example, if anyone will want the same thing. In my case there was only 1 important event, and so the provided snippet worked.

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The short answer is no.

Cocoa is event-driven.

The core of each app is the event loop. On each pass through the event loop, the app handles events added to the event queue. Updating the screen is one such event.

Thus, changes to screen display don't take place until after your code returns, on the next pass through the event loop.

For debugging purposes where you want to figure out what's happening line-by-line, you need to either use the debugger's facilities, or add NSLog statements to your code.