//用pod导入库
pod 'Masonry'

  * //新增约束

-(NSArray *)mas_makeConstraints:(void(^)(MASConstraintMaker *make))block;

  *  //更新约束

-(NSArray *)mas_updateConstraints:(void(^)(MASConstraintMaker *make))block;

  *  //清除之前的所有约束,从新添加最新的约束

-(NSArray *)mas_remakeConstraints:(void(^)(MASConstraintMaker *make))block;