When debugging autorun in what does masking strings mean like h = - & v = - & -?

Question

I think they should relate to the model of struts and springs, but I can not find their mention. When restricting an NSLog they sometimes appear as a description string for the undocumented NSAutoresizingMaskLayoutConstraint class. I noticed at least 3 different types: h=--- , h=--& , h=-&- with horizontal and vertical versions.

They very often appear during debugging using limited layouts.

Answer 1

If you specify automatic masking instead of restrictions or do not specify restrictions at all, then the view will have NSAutoResizingMaskLayoutConstraint restrictions, not NSLayoutConstraints. If you set translatesAutoresizingMaskIntoConstraints to NO , then these restrictions are not displayed. You cannot mix and match in one view, or you get unsatisfactory constraint errors.

I set up a quick test project with various combinations of autoresist masks, and the logging format is pretty simple.

• h= or v= indicates that we are talking about bans in the horizontal or vertical direction.
• - indicates a fixed size
• & indicates flexible size
• Character order represents margin, size, margin

Therefore, h=&-& means that you have left and right margins and a fixed width, v=-&- means fixed upper and lower margins and flexible height, etc.

Answer 2

If you watch the WWDC 2012 video in the "Best Practices for Mastering Auto Layout" section, there is a section where the facilitator mentions that this is a syntax for representations that use autoresist and NOT masks. There is no visual format associated with them, for example for NSLayoutConstraint.

Answer 3

Adding jrturton to the answer, the best information I found to understand the descriptions of constraints is Visual Format documentation, which requires creating constraints in the code. The language is documented as formal grammar, so it may take a minute to absorb it all.

https://developer.apple.com/library/ios/documentation/userexperience/conceptual/AutolayoutPG/VisualFormatLanguage/VisualFormatLanguage.html#//apple_ref/doc/uid/TP40010853-CH3-SW1

Give an example:

 <NSLayoutConstraint:0x10ada8a70 H:|-(44)-[UIButton:0x10ac5dc30] (Names: '|':UIView:0x10ac60470)> 

This is a horizontal orientation constraint ( H:) . The relationship is 44 pixels from the supervisor (|) to UIButton. The named supervisor is UIView ( Names: '|': UIView:) - it is important to know because you do not need to restrict direct viewing

Sixteen values ​​are all valid addresses of your interface elements. When you stop a point in all exceptions and suspend a conflict conflict, you can use the po address to view the constraint object. In my case:

 (lldb) po 0x10ac5dc30 <UIButton: 0x10ac5dc30; frame = (44 199; 30 30); opaque = NO; autoresize = RM+BM; layer = <CALayer: 0x10ac5ddf0>> (lldb) po 0x10ac60470 <UIView: 0x10ac60470; frame = (0 64; 320 504); autoresize = RM+BM; animations = { position=<CABasicAnimation: 0x10ac5ec70>; bounds=<CABasicAnimation: 0x10ac62250>; }; layer = <CALayer: 0x10ac60530>>