iOS: addConstraints: crashing app

问题

Problem

I can't seem to adopt Auto Layout into my existing project.

Details

I was having the same issue before as this question presentViewController: crash on iOS <6 (AutoLayout) but none of the provided answers were a solution for me: I'm using all storyboard views with no xibs. My 'Use Auto Layout' setting is already turned off and I am using nothing but iOS 6.

My view controller was initially crashing, so I set the constraints to be added with a delay and now my app crashes during any addConstraints: call. Worst part is that it won't tell me why.

Code

I will link my code, but its pretty straight forward.

-(void)addAllConstraints
{
    NSDictionary * views = NSDictionaryOfVariableBindings(_memoryImage, _peopleView, _contentHolder, _commentsTableView);
    NSArray * constraints = [NSLayoutConstraint constraintsWithVisualFormat:@"V:[_memoryImage]-50-[_peopleView]-0-[_contentHolder]-0-[_commentsTableView]" options:0 metrics:nil views:views];
    NSLog(@"Views %@, Constraints %@", views, constraints);
    [_peopleView addConstraints:constraints];
    [_memoryImage addConstraints:constraints];
    [_contentHolder addConstraints:constraints];
   [_commentsTableView addConstraints:constraints];
}

App crashes on _peopleView's call to addConstraints. Both the views and the NSLayoutConstraints are successfully created.

Any ideas? Thank you, Happy Holidays.

EDIT:

Adding Crash logs to show that nothing useful is showing:

2012-12-25 10:40:13.936 -----[4955:907] Views {
"_commentsTableView" = "<UITableView: 0x1eb6be00; frame = (0 372; 320 100); clipsToBounds = YES; gestureRecognizers = <NSArray: 0x1e51ce00>; layer = <CALayer: 0x1e51cee0>; contentOffset: {0, 0}>";
"_contentHolder" = "<UIView: 0x1e5c6590; frame = (0 270; 320 112); layer = <CALayer: 0x1e5c27f0>>";
"_memoryImage" = "<UIButton: 0x1e5c4aa0; frame = (0 0; 320 280); opaque = NO; layer = <CALayer: 0x1e5c4b60>>";
"_peopleView" = "<UIView: 0x1f0ceea0; frame = (0 230; 320 50); layer = <CALayer: 0x1f0cf790>>";

Constraints (
"NSLayoutConstraint:0x1e51a880 V:[UIButton:0x1e5c4aa0]-(50)-[UIView:0x1f0ceea0]",
"NSLayoutConstraint:0x1e5ba4e0 V:[UIView:0x1f0ceea0]-(0)-[UIView:0x1e5c6590]",
"NSLayoutConstraint:0x1e51b860 V:[UIView:0x1e5c6590]-(0)-[UITableView:0x1eb6be00]"
)


}  
   (lldb) 

回答1:

Constraints are supposed to be added to the view that is the superview of the subviews. So, if these objects are in your main view, then you should have (and none of the other addConstraints: lines):

[self.view addConstraints:constraints];

Also, your dictionary, views, should be nil terminated (I don't know whether this is necessary or not. I've noticed in an Apple example that they didn't do this, but the function definition shows it with the nil).

来源：https://stackoverflow.com/questions/14032230/ios-addconstraints-crashing-app