xcdoe4.2中，通过ARC来编译，总会遇到一些问题，比如原先使用c语言模块

很多时候，在使用Automatic Reference Counting的是时候，会提示一些很陌生的的错误提示，特别是使用conver to arc后，

 

比如bridged cast 

给你的c代码上面加个_bridged。

 

这里面有个详细的描述，

 

A bridged cast is a C-style cast annotated with one of three keywords:

• (__bridge T) op casts the operand to the destination type T. If T is a retainable object pointer type, then op must have a non-retainable pointer type. If T is a non-retainable pointer type, then op must have a retainable object pointer type. Otherwise the cast is ill-formed. There is no transfer of ownership, and ARC inserts no retain operations.
• (__bridge_retained T) op casts the operand, which must have retainable object pointer type, to the destination type, which must be a non-retainable pointer type. ARC retains the value, subject to the usual optimizations on local values, and the recipient is responsible for balancing that +1.
• (__bridge_transfer T) op casts the operand, which must have non-retainable pointer type, to the destination type, which must be a retainable object pointer type. ARC will release the value at the end of the enclosing full-expression, subject to the usual optimizations on local values.

These casts are required in order to transfer objects in and out of ARC control; see the rationale in the section on conversion of retainable object pointers.

Using a __bridge_retained or __bridge_transfer cast purely to convince ARC to emit an unbalanced retain or release, respectively, is poor form.

 

 

其实，你在apple llvm 的提示下面应该就能看到一些消息的描述，主要是说retain，这里面的bridge有unretained 和retained两种，说到这里面大家应该知道retain的含义了。

 

 

先写到这。

 

其实在这里面，跟多的是一些警告，让我决定很烦。

比如隐式转换，和显示转换。