问题
I'm developing an app with a target of iOS7, and I get the following error when I deploy the app to an iPhone 4.
[NSLayoutConstraint setActive:]: unrecognized selector sent to instance
I looked into this and it turns out that setActive was introduced in iOS8. Question is, what is the alternative to setActive for constraints, circa iOS7? I need to manipulate the constraints programmatically and can't seem to find the answer anywhere.
回答1:
Another way to do this would be to add/remove the constraint from the view:
[myView addConstraint:constraint];
[myView removeConstraint:constraint];
This has been available since iOS 6.0. https://developer.apple.com/library/ios/documentation/UIKit/Reference/UIView_Class/index.html#//apple_ref/occ/instm/UIView/addConstraint:
来源：https://stackoverflow.com/questions/31167248/deactive-nslayoutconstraint-ios7