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Visual Format Language short cut in VFL
a. NSLayoutConstraint.constraintsWithVisualFormat("formatString", options:[NSLayoutFormatOptions], metrics:[String: NSNumber], views:[String: Anyobject]), this is the method we use in VFL, Let dive into the method.
b.the formatString: in this string we use characters like below:
|:stands for superview
-:standard value
V:vertical direction
H: horizontal direction
<= or >=: specify the value relationship
@:specify the priority
and the entire string is like:
"V:|-[componentToLayout(height@priority)]-15-|" this is for vertical direction
"H:|-20-[componentToLayout(width@priority)]-|"this is for horizontal direction
c.the NSLayoutFormatOptions is about to align the different components together, but remember when you in the Vertical direction you can only align the X axis alignment and when you in the Horizontal direction you can only align the Y axis alignment, final the alignment will be used to all components appear in the format string.
d.metrics: this is just a dictionary that used to declare the string used in the format string which stands for some NSNumber value, and we could use NSNumber value directly or constant even computed variable as the value referenced by the string key.
e.views: this is a dictionary that used to declare all the components used in format string like [component], is a type of [String: Anyobject], we use the key string to stands for the component related to the dictionary in the format string.
Sorry guys i‘m using a chinese blog website, so i have no idea if there is a blog i can use in english, please leave any comments below and the related chinese word is "评论"，thank you so much for your reading, and if you have any suggestions please leave it below.
ios - AutoLayout VisualFormatLanguage
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原文地址：http://www.cnblogs.com/geekbang/p/5006814.html
