自动布局以编程方式修改约束乘数

问题描述

如何以编程方式修改约束的乘数?我设置了以下内容:

How can I modify the multiplier of a constraint programmatically? I have set the following:

[self.view addConstraint:[NSLayoutConstraint constraintWithItem:_button attribute:NSLayoutAttributeWidth relatedBy:NSLayoutRelationEqual toItem:self.view attribute:NSLayoutAttributeWidth multiplier:0.5 constant:0.0]];

我需要将其修改为:

[self.view addConstraint:[NSLayoutConstraint constraintWithItem:_button attribute:NSLayoutAttributeWidth relatedBy:NSLayoutRelationEqual toItem:self.view attribute:NSLayoutAttributeWidth multiplier:1.0 constant:0.0]];

推荐答案

正如其他人所说，你必须删除旧的并添加一个新的.如果不想将其存储为属性，只需设置标识符并稍后搜索即可获取它

As others said, you have to delete the old one and add a new one. If you do not want to store it as a property, just set identifier and search to get it later

-(NSLayoutConstraint *)constraintWithIndientifer:(NSString *)identifer InView:(UIView *)view{
    NSLayoutConstraint * constraintToFind = nil;
    for (NSLayoutConstraint * constraint in view.constraints ) {
        if([constraint.identifier isEqualToString:identifer]){
            constraintToFind = constraint;
            break;
        }
    }
    return constraintToFind;
}

然后

NSLayoutConstraint * constraint = [NSLayoutConstraint constraintWithItem:self.yellowView attribute:NSLayoutAttributeWidth relatedBy:NSLayoutRelationEqual toItem:self.view attribute:NSLayoutAttributeWidth multiplier:0.5 constant:0.0];
constraint.identifier = @"1234";
[self.view addConstraint:constraint];

那么你可以得到这个

NSLayoutConstraint * constraint = [self constraintWithIndientifer:@"1234" InView:self.view];

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