Masonry的官方是这么描述自己的。

• Masonry is a light-weight layout framework which wraps AutoLayout with a nicer syntax. Masonry has its own layout DSL which provides a chainable way of describing your NSLayoutConstraints which results in layout code that is more concise and readable. Masonry supports iOS and Mac OS X.

• However if you're using Swift in your project, we recommend using SnapKit as it provides better type safety with a simpler API.
  Masonry ： https://github.com/SnapKit/Masonry
  SnapKit： https://github.com/SnapKit/SnapKit

2.1 Basic Grammar

mas_makeConstraints
mas_updateContraints
mas_remakeContraints

1 基础写法：

    [redView mas_makeConstraints:^(MASConstraintMaker *make) {
        make.centerX.equalTo(self.view.mas_centerX);
        make.centerY.equalTo(self.view.mas_centerY);
//equalTo 后面要求跟一个OC对象的数据，所以需要对数字进行包装。@将数字变成了NSNumber 类型。
        make.width.equalTo(@200);
        make.height.equalTo(@50);
    }];

make.xxxx属性.equalTo(参照对象.mas_属性【如果相同，可以省略】).offset(常数)

2 进阶写法

• NSNumber只能装基本数据类型
• NSValue可以装结构体等数据类型

// 进阶语法
    [redView mas_makeConstraints:^(MASConstraintMaker *make) {
        make.center.equalTo(self.view);
        make.size.equalTo([NSValue valueWithCGSize:CGSizeMake(200, 100)]);
    }];

3 自动装箱的写法

• 装箱：把一个基本数据类型转换成为对象类型的过程叫做“装箱”，或者“包装”。

    [redView mas_makeConstraints:^(MASConstraintMaker *make) {
        make.center.equalTo(self.view);
        make.size.mas_equalTo(CGSizeMake(100, 200));
    }];

4 Masonry的练习

4.1 设置居中

// create a imageview in the center of scrollview UIImageView *imageView = [[UIImageView alloc]initWithImage:[UIImage imageNamed:@"001"]]; [scrollView addSubview:imageView]; [imageView mas_makeConstraints:^(MASConstraintMaker *make) { make.center.equalTo(scrollView); make.size.mas_equalTo(CGSizeMake(140, 140)); }];

4.2 让一个view略小于其superView(边距为20)

• 假设redView 是View 的子控件

[redView mas_makeConstraints:^(MASConstraintMaker *make) { make.top.equalTo(self.view.mas_top).offset(20); make.left.equalTo(self.view.mas_left).offset(20); make.bottom.equalTo(self.view.mas_bottom).offset(-20); make.right.equalTo(self.view.mas_right).offset(-20); }];

• 当约束控件属性和参照控件属性相同的时候，参照控件的属性可以不写

    [redView mas_makeConstraints:^(MASConstraintMaker *make) {
        make.top.equalTo(self.view).offset(20);
        make.left.equalTo(self.view).offset(20);
        make.bottom.equalTo(self.view).offset(-20);
        make.right.equalTo(self.view.).offset(-20);
    }];

• 如果参照的是自己的父控件，参照控件也可以省略不写

[imageView mas_makeConstraints:^(MASConstraintMaker *make) { make.top.offset(20); make.left.offset(20); make.bottom.offset(20); make.right.offset(20); }];

• 如果多个属性的offset数值一样，属性也可以连写

    [imageView mas_makeConstraints:^(MASConstraintMaker *make) {
        make.top.left.offset(20);
        make.bottom.right.offset(20);
    }];

4.3 通过更简单的内边距形式修改控件的位置和大小

    [imageView mas_makeConstraints:^(MASConstraintMaker *make) {
        make.edges.mas_offset(UIEdgeInsetsMake(20, 20, 20, 20));
    }];

5. 更新及重建约束

• update是更新约束：如果之前已经添加过，那么就是更新约束。但是如果之前没有设置过，有可能会造成约束冲突。
• 修改完约束之后，需要让子控件根据约束调整frame才能生效

[imageView mas_updateConstraints:^(MASConstraintMaker *make) {
        make.right.offset(-50);
    }];
    
//    播放两秒动画
    [UIView animateWithDuration:2 animations:^{
        //让这个控件立刻根据约束修改自己的frame
        [imageView layoutIfNeeded];
    }];

6. Masonry的两个宏

• 如果想在使用Masonry框架时，省略mas_的前缀，需要定义以下宏:

• #define MAS_SHORTHAND

• 让equalTo,offset都带有自动装箱功能，需要定义以下宏：

• #define MAS_SHORTHAND_GLOBALS