zoukankan      html  css  js  c++  java
  • Placement of class definition and prototype

    When I create a function, I can put the code for it after main if I put the prototype above main. For example,

    int myFunction(int a)
    {
    return(a); 
    }

    would have the prototype..

    int myFunction(int a);

    above main.

    However, I have not been able to get this to work for a class definition.

    If I put …

    class myClass
    {
    
    };

    below main,

    I get an error if I put

    class myClass;

    above main. The error occurs where the class is used within main, and the error is "unknown type name." That's with the c++ compiler that is part of Xcode.

    What kind of prototype should I enter above main if the class definition is below main?



    When you call a function and the definition is not available, the compiler doesn't have to know the contents in order to continue evaluating the rest of the code (eg: stack usage at the call site). It only needs to know the function's signature to ensure the correct parameters are going to be passed into the function. The linker will hook up the actual address for the function call after the compiler is done.

    However when you are using a class it has to know about the details of it - not just that it exists - because it'll need to ensure proper layout on the stack, what parameters are required for the constructor, etc.

    The details of the class' functions are of course like regular functions - it just needs the signature to work with - they can be defined later.


  • 相关阅读:
    NET基础课--XML基础
    NET基础课--WinForm开发推荐3
    NET基础课--JIT编译器如何工作1
    NET基础课--异常处理X
    NSURLRequest POST方式请求服务器示例
    iOS开发网络篇—NSURLConnection基本使用
    AFNetworking封装思路简析
    IOS NSURLRequest 设置 Header
    AFNetworking3.0为何弃用了NSURLConnection
    iOS开发多线程篇—GCD介绍
  • 原文地址:https://www.cnblogs.com/vigorz/p/10499205.html
Copyright © 2011-2022 走看看