ios autolayout中NSLayoutAttributeLeft(Right)与NSLayoutAttributeLeading(Trailing)区别

1、

原文地址：http://blog.csdn.net/yueyeguzhuo/article/details/45310499

Autolayout使用的时候，相信很多童鞋都有这个疑惑，为啥布局里面会有如下的感觉相同的选项呢

    NSLayoutAttributeLeft ,
    NSLayoutAttributeRight,
   
    NSLayoutAttributeLeading,
    NSLayoutAttributeTrailing,

下面来说一下区别：

NSLayoutAttributeLeft 和 NSLayoutAttributeRight 代表从左右进行布局

NSLayoutAttributeLeading和 NSLayoutAttributeTrailing 代表从前后进行布局


在天朝 NSLayoutAttributeLeft 和 NSLayoutAttributeLeading 是一个效果的，布局习惯从左到右

但在有些国家地区，NSLayoutAttributeRight和NSLayoutAttributeLeading 是一个效果，布局习惯从右往左

使用推荐：NSLayoutAttributeLeading和 NSLayoutAttributeTrailing （比较常用）


2、

http://stackoverflow.com/questions/19971508/difference-between-nslayoutattributeleft-vs-nslayoutattributeleading


44 down vote accepted

"Leading" is not always means "Left". For RTL-written languages (locales) leading edge of the object’s alignment rectangle will be located at the right side of the object.

Quote from Auto Layout Guide:

The attributes leading and trailing are the same as left and right for left-to-right languages such as English, but in a right-to-left environment such as Hebrew or Arabic, leading and trailing are the same as right and left. When you create constraints, leading and trailing are the default values. You should usually use leading and trailing to make sure your interface is laid out appropriately in all languages, unless you’re making constraints that should remain the same regardless of language (such as the order of master and detail panes in a split view).

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