Masonry 优先级（简单明了）

一、AutoLayout有两个重要的属性：

1.Content Compression Resistance 百度翻译（内容压缩抗力）
2.Content Hugging 百度翻译(内容拥抱)

二、解释

Content Compression Resistance = 变大！（保持自己更大）

这个属性的优先级（Priority）越高，越不“容易”被压缩。也就是说，当整体的空间装不下所有的View的时候，Content Compression Resistance优先级越高的，现实的内容越完整。

[self.labelTwo setContentCompressionResistancePriority:UILayoutPriorityDefaultHighforAxis:UILayoutConstraintAxisHorizontal];

Content Hugging = 抱紧！（保持自己更小）

这个属性的优先级越高，整个View就要越“抱紧”View里面的内容。也就是View的大小不会随着父级View的扩大而扩大。

[self.labelOne setContentHuggingPriority:UILayoutPriorityDefaultHighforAxis:UILayoutConstraintAxisHorizontal];

 >参数一：(UILayoutPriority)
 >设置优先级等级，数值越大，优先级越高。
 >UILayoutPriorityRequired           == 1000；
 >UILayoutPriorityDefaultHigh        == 750；
 >UILayoutPriorityDefaultLow         == 250；
 >UILayoutPriorityFittingSizeLevel   == 50；


>参数二：(UILayoutConstraintAxis)
>百度翻译(Axis：轴线。意思是你添加的优先级是Horizontal还是Vertical)
 >UILayoutConstraintAxisHorizontal
 >UILayoutConstraintAxisVertical

三、代码部分

#import "ViewController.h"
#import "Masonry.h"

@interface ViewController ()

@property(nonatomic,strong) UILabel * labelOne;
@property(nonatomic,strong) UILabel * labelTwo;

@end

@implementation ViewController


- (void)initUI
{
    [self.view addSubview:self.labelOne];
    [self.labelOne mas_makeConstraints:^(MASConstraintMaker *make) {
        make.left.equalTo(self.view.mas_left).with.offset(20);
        make.top.equalTo(self.view.mas_top).with.offset(20);
    }];
    
    [self.view addSubview:self.labelTwo];
    [self.labelTwo mas_makeConstraints:^(MASConstraintMaker *make) {
        make.left.equalTo(_labelOne.mas_right);
        make.right.equalTo(self.view.mas_right);
        make.top.equalTo(self.view.mas_top).with.offset(20);
        make.height.equalTo(_labelOne);
    }];
    
    [self.labelOne setContentHuggingPriority:UILayoutPriorityDefaultHigh forAxis:UILayoutConstraintAxisHorizontal];
    /**参数一：(UILayoutPriority)
     UILayoutPriorityRequired
     UILayoutPriorityDefaultHigh
     UILayoutPriorityDefaultLow
     UILayoutPriorityFittingSizeLevel
     */
    
    /**参数二：(UILayoutConstraintAxis)
     UILayoutConstraintAxisHorizontal
     UILayoutConstraintAxisVertical
     */
    [self.labelTwo setContentCompressionResistancePriority:UILayoutPriorityDefaultHigh forAxis:UILayoutConstraintAxisHorizontal];
}

- (void)viewDidLoad {
    [super viewDidLoad];
    [self initUI];
}

- (UILabel *)labelOne{
    if (!_labelOne) {
        self.labelOne = [[UILabel alloc] init];
        self.labelOne.text = @"这是labelOne";
        self.labelOne.backgroundColor = [UIColor redColor];
    }
    return _labelOne;
}

- (UILabel *)labelTwo{
    if (!_labelTwo) {
        self.labelTwo = [[UILabel alloc] init];
        self.labelTwo.text = @"这是labelTwo";
        self.labelTwo.backgroundColor = [UIColor greenColor];
    }
    return _labelTwo;
}
@end

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