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([email protected])]-15-|" this is for vertical direction
"H:|-20-[componentToLayout([email protected])]-|"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.
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