将视图位置设置为superview时Autolayout崩溃

Question

我在设置视图位置时遇到崩溃

  

2014-10-06 15：25：01.896 sample [21174：60b]视图层次结构没有为约束准备：

When added to a view, the constraint's items must be descendants of that view (or the view itself). This will crash if the constraint needs to be resolved before the view hierarchy is assembled. Break on -[UIView _viewHierarchyUnpreparedForConstraint:] to debug.

2014-10-06 15：25：01.898 sample [21174：60b]视图层次结构没有为约束准备：

When added to a view, the constraint's items must be descendants of that view (or the view itself). This will crash if the constraint needs to be resolved before the view hierarchy is assembled. Break on -[UIView _viewHierarchyUnpreparedForConstraint:] to debug.

这是代码..

    self.redView = [UIView new];
self.redView.translatesAutoresizingMaskIntoConstraints = NO;
self.redView.backgroundColor = [UIColor colorWithRed:0.95 green:0.47 blue:0.48 alpha:1.0];

self.yellowView = [UIView new];
self.yellowView.translatesAutoresizingMaskIntoConstraints = NO;
self.yellowView.backgroundColor = [UIColor colorWithRed:1.00 green:0.83 blue:0.58 alpha:1.0];

[self.view addSubview:self.redView];
[self.view addSubview:self.yellowView];

    NSDictionary *viewDictionary = @{@"redView": self.redView};

NSArray *constraints_H = [NSLayoutConstraint constraintsWithVisualFormat:@"V:[redView(100)]" options:0 metrics:nil views:viewDictionary];
NSArray *constraints_V = [NSLayoutConstraint constraintsWithVisualFormat:@"H:[redView(100)]" options:0 metrics:nil views:viewDictionary];
NSArray *constraint_POS_V = [NSLayoutConstraint constraintsWithVisualFormat:@"V:|-30-[redView]"
                                                                    options:0
                                                                    metrics:nil
                                                                      views:viewDictionary];

NSArray *constraint_POS_H = [NSLayoutConstraint constraintsWithVisualFormat:@"H:|-20-[redView]"
                                                                    options:0
                                                                    metrics:nil
                                                                      views:viewDictionary];
[self.redView addConstraints:constraints_H];
[self.redView addConstraints:constraints_V];
[self.redView addConstraints:constraint_POS_V];
[self.redView addConstraints:constraint_POS_H];