Visual format language（1）

来源：互联网发布：淘宝保证金计划不符合编辑：程序博客网时间：2024/06/05 16:25

需求：添加一个控件，高度40，距离顶部，左边，右边 20

    // 1.创建控件    UIView *blueView = [[UIView alloc] init];    [self.view addSubview:blueView];    blueView.backgroundColor = [UIColor blueColor];    //不要将AutoresizingMask转为Autolayout的约束    blueView.translatesAutoresizingMaskIntoConstraints = NO;        // 2.添加约束    //水平方向约束    NSString *vfl = @"H:|-20-[blueView]-20-|";    NSDictionary *views = @{@"blueView" : blueView};    NSArray *constraints = [NSLayoutConstraint constraintsWithVisualFormat:vfl options:kNilOptions metrics:nil views:views];    [self.view addConstraints:constraints];        //垂直方向约束    NSString *vfl2 = @"V:|-20-[blueView(40)]";    NSArray *constraints2 = [NSLayoutConstraint constraintsWithVisualFormat:vfl2 options:kNilOptions metrics:nil views:views];    [self.view addConstraints:constraints2];

优化后的代码：

    // 1.创建控件    UIView *blueView = [[UIView alloc] init];    [self.view addSubview:blueView];    blueView.backgroundColor = [UIColor blueColor];    //不要将AutoresizingMask转为Autolayout的约束    blueView.translatesAutoresizingMaskIntoConstraints = NO;        //间距    NSNumber *margin = @20;        // 2.添加约束    //水平方向约束    NSString *vfl = @"H:|-margin-[blueView]-margin-|";    NSDictionary *views = NSDictionaryOfVariableBindings(blueView);    NSDictionary *metrics = NSDictionaryOfVariableBindings(margin);    NSArray *constraints = [NSLayoutConstraint constraintsWithVisualFormat:vfl options:kNilOptions metrics:metrics views:views];    [self.view addConstraints:constraints];        //垂直方向约束    NSNumber *height = @40;    NSString *vfl2 = @"V:|-margin-[blueView(height)]";    NSDictionary *metrics2 =NSDictionaryOfVariableBindings(margin,height);    NSArray *constraints2 = [NSLayoutConstraint constraintsWithVisualFormat:vfl2 options:kNilOptions metrics:metrics2 views:views];    [self.view addConstraints:constraints2];

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