View+MASAddtions
使用Masonry主要用到的是UIView+MASAddtions的分类，这里面最主要的几个类如下
- 常用的类
- MASViewAttribute 保存某个属性的类
- MASConstraintMaker 用于设置约束
这里一个很有意思的知识点，就是并没有直接写成UIView的分类，因为Masonry同事适配iOS、OSX，这样定义一个宏就可以一份代码不用区分具体是什么环境了
2、 MASUtilities.h 知识点1
#if TARGET_OS_IPHONE || TARGET_OS_TV
#import <UIKit/UIKit.h>
#define MAS_VIEW UIView
#define MAS_VIEW_CONTROLLER UIViewController
#define MASEdgeInsets UIEdgeInsets
typedef UILayoutPriority MASLayoutPriority;
static const MASLayoutPriority MASLayoutPriorityRequired = UILayoutPriorityRequired;
static const MASLayoutPriority MASLayoutPriorityDefaultHigh = UILayoutPriorityDefaultHigh;
static const MASLayoutPriority MASLayoutPriorityDefaultMedium = 500;
static const MASLayoutPriority MASLayoutPriorityDefaultLow = UILayoutPriorityDefaultLow;
static const MASLayoutPriority MASLayoutPriorityFittingSizeLevel = UILayoutPriorityFittingSizeLevel;
#elif TARGET_OS_MAC
#import <AppKit/AppKit.h>
#define MAS_VIEW NSView
#define MASEdgeInsets NSEdgeInsets
typedef NSLayoutPriority MASLayoutPriority;
static const MASLayoutPriority MASLayoutPriorityRequired = NSLayoutPriorityRequired;
static const MASLayoutPriority MASLayoutPriorityDefaultHigh = NSLayoutPriorityDefaultHigh;
static const MASLayoutPriority MASLayoutPriorityDragThatCanResizeWindow = NSLayoutPriorityDragThatCanResizeWindow;
static const MASLayoutPriority MASLayoutPriorityDefaultMedium = 501;
static const MASLayoutPriority MASLayoutPriorityWindowSizeStayPut = NSLayoutPriorityWindowSizeStayPut;
static const MASLayoutPriority MASLayoutPriorityDragThatCannotResizeWindow = NSLayoutPriorityDragThatCannotResizeWindow;
static const MASLayoutPriority MASLayoutPriorityDefaultLow = NSLayoutPriorityDefaultLow;
static const MASLayoutPriority MASLayoutPriorityFittingSizeCompression = NSLayoutPriorityFittingSizeCompression;
#endif
3、 获取布局属性，直接用MASViewAttribute得到
#pragma mark - NSLayoutAttribute properties
- (MASViewAttribute *)mas_left {
return [[MASViewAttribute alloc] initWithView:self layoutAttribute:NSLayoutAttributeLeft];
}
4、获取两个类最近的共同父类，使用了一个2层递归遍历,思路是用第一个View，也就是当前View的每一个父类（包含第一个类自己）与第二个View的所有父类（包括第二个类自己）进行比较，这样只要有相等的则是共同的父类，复杂度为n*m
不知道具体效率怎么样
#pragma mark - heirachy
- (instancetype)mas_closestCommonSuperview:(MAS_VIEW *)view {
MAS_VIEW *closestCommonSuperview = nil;
MAS_VIEW *secondViewSuperview = view;
while (!closestCommonSuperview && secondViewSuperview) {
MAS_VIEW *firstViewSuperview = self;
while (!closestCommonSuperview && firstViewSuperview) {
if (secondViewSuperview == firstViewSuperview) {
closestCommonSuperview = secondViewSuperview;
}
firstViewSuperview = firstViewSuperview.superview;
}
secondViewSuperview = secondViewSuperview.superview;
}
return closestCommonSuperview;
}
5、 添加约束的过程就是以下几个过程
- 设置不响应Autoresizing
- 创建一个MASConstraintMaker实例
- 通过block把约束保存到MASConstraintMaker里
- 然后调用MASConstraintMaker的install方法把约束加到View上并返回一个数组
- 修改就是给maker添加一个updateExisting=YES，重置就是给removeExisting=YES，默认设置时这两个属性都是NO
- 返回的数组是所有添加的MASContriaints
- (NSArray *)mas_makeConstraints:(void(^)(MASConstraintMaker *))block {
self.translatesAutoresizingMaskIntoConstraints = NO;
MASConstraintMaker *constraintMaker = [[MASConstraintMaker alloc] initWithView:self];
block(constraintMaker);
return [constraintMaker install];
}
