Masonry 原理与使用说明

原理：

1）约束生成；MASConstraintMaker；

2）缺省补齐：

- (void)setSecondViewAttribute:(id)secondViewAttribute {

if ([secondViewAttribute isKindOfClass:NSValue.class]) {

[self setLayoutConstantWithValue:secondViewAttribute];

} else if ([secondViewAttribute isKindOfClass:MAS_VIEW.class]) {

_secondViewAttribute = [[MASViewAttribute alloc] initWithView:secondViewAttribute layoutAttribute:self.firstViewAttribute.layoutAttribute];

} else if ([secondViewAttribute isKindOfClass:MASViewAttribute.class]) {

_secondViewAttribute = secondViewAttribute;

} else {

NSAssert(NO, @"attempting to add unsupported attribute: %@", secondViewAttribute);

}

}

3）寻找约束添加视图，并添加

if (self.secondViewAttribute.view) {

MAS_VIEW *closestCommonSuperview = [self.firstViewAttribute.view mas_closestCommonSuperview:self.secondViewAttribute.view];

NSAssert(closestCommonSuperview,

@"couldn't find a common superview for %@ and %@",

self.firstViewAttribute.view, self.secondViewAttribute.view);

self.installedView = closestCommonSuperview;

} else if (self.firstViewAttribute.isSizeAttribute) {

self.installedView = self.firstViewAttribute.view;

} else {

self.installedView = self.firstViewAttribute.view.superview;

}

4）

（1）绝对尺寸信息添加到自身；

（2）绝对布局数据添加到父视图；

（3）参考系属性缺失补全为目标属性。