这几天专心写一下pop动画
好的代码贴在下方:
```objc
POPAnimatableProperty *constantProperty = [POPAnimatableProperty propertyWithName:@"constant" initializer:^(POPMutableAnimatableProperty *prop){
prop.readBlock = ^(NSLayoutConstraint *layoutConstraint, CGFloat values[]) {
values[0] = [layoutConstraint constant];
};
prop.writeBlock = ^(NSLayoutConstraint *layoutConstraint, const CGFloat values[]) {
[layoutConstraint setConstant:values[0]];
};
}];
POPSpringAnimation *constantAnimation = [POPSpringAnimation animation];
constantAnimation.property = constantProperty;
constantAnimation.fromValue = @(self.bottomSpace.constant);
constantAnimation.toValue = @(0);
[self.bottomSpace pop_addAnimation:constantAnimation forKey:@"constantAnimation"];
```
