Masonry简介

GitHub链接:
https://github.com/SnapKit/Masonry

Harness the power of AutoLayout NSLayoutConstraints with a simplified, chainable and 
expressive syntax. Supports iOS and OSX Auto Layout

基于 AutoLayout NSLayoutConstraints的一个更加简化,链式和更容易表达的语法.支持iOS和OSX自动布局.

Masonry 
Masonry is still actively maintained, we are committed to fixing bugs and merging 
good quality PRs from the wider community.However, if you're using Swift in your 
project, we recommend using [SnapKit](https://github.com/SnapKit/SnapKit) 
as it provides better type safety with a simpler API.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.For examples take a look at the **Masonry iOS Examples** project in the 
Masonry workspace. You will need to run pod install after downloading.

Masonry仍在积极维护，我们致力于修复bug，在他人的帮助下�加入了更好的特性。�如果,你使用的是Swift在你的项目中，我们建议使用
SnapKit(https://github.com/SnapKit/SnapKit)，
因为它提供了�一个更简单,更好类型的安全API。
Masonry是一个轻量级的布局框架，它�通过一个更友好的语法封装的自动布局。Masonry�通过�本身布局的DSL(Domain-Specific Language可能不准确),
用一个链式语法描述你的NSLayoutConstraints,� 使你的布局代码更加简洁易读.Masonry支持iOS和Mac OS X.
�如果你想看看Masonry在iOS的demo工程。您将需要在下载后安装运行。

What's wrong with NSLayoutConstraints?

这个NSLayoutConstraints到底有什么问题呢?

Under the hood Auto Layout is a powerful and flexible way of organising and laying 
out your views. However creating constraints from code is verbose and not very 
descriptive. Imagine a simple example in which you want to have a view fill its 
superview but inset by 10 pixels on every side

在底层用Auto Layout来组织和布局view是一个强有力和灵活的方式,然而创建约束代码冗长，不容易去描述。想象一个简单的例子，�一个父视图上的有一个子视图,让这个子视图4个边距离父视图都有10px的大小.

UIView *superview = self;UIView *view1 = [[UIView alloc] init];
view1.translatesAutoresizingMaskIntoConstraints = NO;
view1.backgroundColor = [UIColor greenColor];
[superview addSubview:view1];
UIEdgeInsets padding = UIEdgeInsetsMake(10, 10, 10, 10);
[superview addConstraints:@[ 
//view1 constraints 
[NSLayoutConstraint constraintWithItem:view1 
                             attribute:NSLayoutAttributeTop 
                             relatedBy:NSLayoutRelationEqual 
                                toItem:superview 
                             attribute:NSLayoutAttributeTop 
                            multiplier:1.0
                              constant:padding.top],
[NSLayoutConstraint constraintWithItem:view1 
                             attribute:NSLayoutAttributeLeft 
                             relatedBy:NSLayoutRelationEqual 
                                toItem:superview 
                             attribute:NSLayoutAttributeLeft
                            multiplier:1.0 
                              constant:padding.left], 
[NSLayoutConstraint constraintWithItem:view1
                             attribute:NSLayoutAttributeBottom
                             relatedBy:NSLayoutRelationEqual 
                                toItem:superview 
                             attribute:NSLayoutAttributeBottom 
                            multiplier:1.0 
                              constant:-padding.bottom], 
[NSLayoutConstraint constraintWithItem:view1
                             attribute:NSLayoutAttributeRight 
                             relatedBy:NSLayoutRelationEqual 
                                toItem:superview 
                             attribute:NSLayoutAttributeRight 
                            multiplier:1 
                               constant:-padding.right],
 ]];

Even with such a simple example the code needed is quite verbose and quickly becomes 
unreadable when you have more than 2 or 3 views. Another option is to use Visual 
Format Language (VFL), which is a bit less long winded. However the ASCII type syntax 
has its own pitfalls and its also a bit harder to animate as  NSLayoutConstraint 
constraintsWithVisualFormat:returns an array.

即使是这样一个简单的例子Auto Layout需要的代码很冗长。很快当你有超过2或3次代码的约束就会变得晦涩。另一种选择是使用Visual格式语言（VFL），只是比上面代码少了一点。�但是，ASCII类型的语法都有自己的缺陷和和一点点难度，因为
NSLayoutConstraint constraintsWithVisualFormat动画：返回一个数组。

Prepare to meet your Maker!

准备你一切的需要吧!

Heres the same constraints created using MASConstraintMaker

下面是使用MASConstraintMaker创建相同的约束

UIEdgeInsets padding = UIEdgeInsetsMake(10, 10, 10, 10);
[view1 mas_makeConstraints:^(MASConstraintMaker *make)
 { 
make.top.equalTo(superview.mas_top).with.offset(padding.top); 
//with is an optional semantic filler 
make.left.equalTo(superview.mas_left).with.offset(padding.left); 
make.bottom.equalTo(superview.mas_bottom).with.offset(-padding.bottom); 
make.right.equalTo(superview.mas_right).with.offset(-padding.right);
}];

Or even shorter
甚至更短
[view1 mas_makeConstraints:^(MASConstraintMaker *make) { 
make.edges.equalTo(superview).with.insets(padding);
}];

Also note in the first example we had to add the constraints to the superview 
[superview addConstraints:.... Masonry however will automagically add constraints 
to the appropriate view.

�同时，在第一个例子中，我们不得不约束添加到superview[superview addConstraints：....但是视图
会被Masonry自动添加适当的约束.

Masonry will also call 
view1.translatesAutoresizingMaskIntoConstraints = NO;for you.

Masonry会为你调用
view1.translatesAutoresizingMaskIntoConstraints = NO.

待续.....
@erbai 安禹丞同学校对