GitHub鏈接:
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的一個更加簡化,鏈式和更容易表達的語法.支持iOS和OSX自動布局.

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仍在積極維護，我們致力于修復bug，在他人的幫助下加入了更好的特性。如果,你使用的是Swift在你的項目中，我們建議使用
SnapKit(https://github.com/SnapKit/SnapKit)，
因為它提供了一個更簡單,更好類型的安全API。
Masonry是一個輕量級的布局框架，它通過一個更友好的語法封裝的自動布局。Masonry通過本身布局的DSL(Domain-Specific Language可能不準確),
用一個鏈式語法描述你的NSLayoutConstraints, 使你的布局代碼更加簡潔易讀.Masonry支持iOS和Mac OS X.
如果你想看看Masonry在iOS的demo工程。您將需要在下載后安裝運行。

What's wrong with NSLayoutConstraints?

這個NSLayoutConstraints到底有什么問題呢?

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

在底層用Auto Layout來組織和布局view是一個強有力和靈活的方式,然而創建約束代碼冗長，不容易去描述。想象一個簡單的例子，一個父視圖上的有一個子視圖,讓這個子視圖4個邊距離父視圖都有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.

即使是這樣一個簡單的例子Auto Layout需要的代碼很冗長。很快當你有超過2或3次代碼的約束就會變得晦澀。另一種選擇是使用Visual格式語言（VFL），只是比上面代碼少了一點。但是，ASCII類型的語法都有自己的缺陷和和一點點難度，因為
NSLayoutConstraint constraintsWithVisualFormat動畫：返回一個數組。

Prepare to meet your Maker!

準備你一切的需要吧!

Heres the same constraints created using MASConstraintMaker

下面是使用MASConstraintMaker創建相同的約束

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.

同時，在第一個例子中，我們不得不約束添加到superview[superview addConstraints：....但是視圖
會被Masonry自動添加適當的約束.

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

Masonry會為你調用
view1.translatesAutoresizingMaskIntoConstraints = NO.