OC clang-rewrite-objc detailed explanation

OC http://www.jianshu.com/p/c2dabb4fd761

The syntax of block looks special, but it is actually handled as very ordinary C language code. Here we borrow the ability of the clang compiler: the ability to convert it into our readable source code. The console command is: clang -rewrite-objc source code filename.

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         int 
         main(){ 
           
         void 
         (^blk)( 
         void 
         ) = ^{printf( 
         "block\n" 
         );}; 
        
         blk(); 
        
         return 
         0 
         ; 
        
         }

After clang -rewrite-objc, the code programming looks like this (after simplifying the code, readers can search for keywords to find in the generated file):

We all know that we can learn the Objective-C programming language through Xcode , but can we learn Objective-C without the IDE of XCode? Of course it is possible.

As a programmer, you should know that any programming language is inseparable from a compiler, and OC is no exception. We can find through Du Niang’s search that the default compiler of XCode is clang, so the question is, can I directly compile and run a piece of OC code through the clang command? Of course it is possible.

For a detailed introduction to the XCode compiler, please refer to this article: Compiler

The following will describe how to create a Hello Word program through the text editor in Mac OS, and compile and run it through the clang command.

step 1

Open the "Text Editing" tool, enter the following code, and save it in plain text format. The file name is HelloWord.m, and the path is optional.

<code class="objectivec"><span class="hljs-preprocessor" style="color: rgb(68, 68, 68);">#import <span class="hljs-title"><Foundation/Foundation.h></span></span>
<span class="hljs-keyword" style="color: rgb(0, 0, 136);">int</span> main(<span class="hljs-keyword" style="color: rgb(0, 0, 136);">int</span> argc, <span class="hljs-keyword" style="color: rgb(0, 0, 136);">const</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136);">char</span> * argv[])
{ 
  <span class="hljs-keyword" style="color: rgb(0, 0, 136);">@autoreleasepool</span> 
  { 
     <span class="hljs-built_in" style="color: rgb(102, 0, 102);">NSLog</span>(<span class="hljs-string" style="color: rgb(0, 136, 0);">@"Hello, OC!"</span>); 
  }
  <span class="hljs-keyword" style="color: rgb(0, 0, 136);">return</span> <span class="hljs-number" style="color: rgb(0, 102, 102);">0</span>;
}</code>

步骤2

接下来可以利用“终端”将HelloWord.m文件编译成可执行文件了，具体步骤：
1.打开“终端”
2.通过cd命令进入HelloWord.m文件所在目录
3.使用clang命令对HelloWord.m文件进行编译
最后生成HelloWord可执行文件，如下图所示。

图1

$ clang -fobjc-arc -framework Foundation HelloWord.m -o HelloWord

有几个地方需要注意一下：

$符号是终端命令提示符，不是需要输入的内容
-fobjc-arc表示编译器需要支持ARC特性
-framework Foundation表示引用Foundation框架
HelloWord.m为需要进行编译的源代码文件
-o HelloWord indicates the file name of the output executable file

step 3

After the executable file is generated, the file can be executed in the terminal, and the command entered is as follows:

$ ./HelloWord

The execution result is as follows:

figure 2

In addition, you can directly double-click to run the HelloWord executable file just generated, and the running result is the same as the above running result.

image 3

So far, through a few simple clang commands, you can compile and run a simple Objective-C code of HelloWord.

Text/Kevin丨Wang (the author of the short book)
Link to the original text: http://www.jianshu.com/p/c2dabb4fd761
The copyright belongs to the author. For reprinting, please contact the author for authorization and mark "the author of the short book".