iOS7: Calling -makeConstraints: order seems to matter

[BigAB]

iOS7 Bug?

Maybe it is my misunderstanding about how AutoLayout or Masonry work, but it seems to me like the order of calling -makeContraints: in iOS7 is somehow order dependant.

Here is a very simple example:

Expected Result

A very simple view, with a yellow view on top and a blue view on bottom:
Expected Result (Gist)

[blueView makeConstraints:^(MASConstraintMaker *make) {
    make.top.equalTo(yellowView.bottom).offset(padding);
    make.bottom.equalTo(superview.bottom).offset(-padding);
    make.left.equalTo(superview.left).offset(padding);
    make.right.equalTo(superview.right).offset(-padding);
  }];

[yellowView makeConstraints:^(MASConstraintMaker *make) {
    make.top.greaterThanOrEqualTo(superview.top).offset(padding);
    make.left.equalTo(superview.left).offset(padding);
    make.right.equalTo(superview.right).offset(-padding);
    make.height.equalTo(@100);
}];

Possible Bug

All I do is switch the order -makeContraints: is called, calling yellowView first :
Possible Bug Result (Gist)

[yellowView makeConstraints:^(MASConstraintMaker *make) {
    make.top.greaterThanOrEqualTo(superview.top).offset(padding);
    make.left.equalTo(superview.left).offset(padding);
    make.right.equalTo(superview.right).offset(-padding);
    make.height.equalTo(@100);
}]

[blueView makeConstraints:^(MASConstraintMaker *make) {
    make.top.equalTo(yellowView.bottom).offset(padding);
    make.bottom.equalTo(superview.bottom).offset(-padding);
    make.left.equalTo(superview.left).offset(padding);
    make.right.equalTo(superview.right).offset(-padding);
}];

On iOS6 this seems to work fine.
So is this a bug or am I missing something?

[cloudkite]

Firstly thanks for the detailed issue!

It's probably due to a implementation change in how iOS7 handles ambiguous constraints, do you get any console messages?.
I think your problem lies in the fact you are using make.top.greaterThanOrEqualTo(superview.top).offset(padding);
have you tried using make.top.equalTo(superview.top).offset(padding); instead?

By using make.top.greaterThanOrEqualTo(superview.top).offset(padding); you are basically telling Auto Layout this view can be anywhere vertically as long as it's more than padding.

greaterThanOrEqualTo is best used if you have more than one constraint on that NSLayoutAttribute otherwise Auto Layout may treat it as ambiguous which has weird results.

Let me know if that helps

[BigAB]

There are no console messages.

It may be ambiguous as, you're right, changing it to equalTo does seem to fix the issue.

I did find it odd that it worked in iOS6 but not iOS7, but as you said, maybe they just handle ambiguous layout differently.

Thanks for your time.