从函数返回两个值 [英] Return two values from a Function

问题描述

如何从返回类型函数中获得两个值?

请举个例子.

How can I get two values from a return type function?

Please give an example.

推荐答案

我认为，最简单的选择是使用SA的答案:

I think the easiest choice for you is to use SA''s answer:

//define a result structure
struct RESULT
{
    //add as many members as you want here...
    int result1;
    float result2;
};

//this function returns a struct
RESULT function()
{
    //declare the value you will return
    RESULT returnValue;
    //fill the fields
    returnValue.result1 = 5;
    returnValue.result2 = 12.3f;
    //return the value
    return returnValue;
}

要返回两个值，您可以做一些不同的事情:

1.返回一个对象.定义一个类并返回该类的实例.
2.返回一个结构.
3.返回一个数组.
4.使用参考参数(尽管这并不是最纯粹的含义).

您之前收到的答案很好.

HTH！

In order to return two values you can do several different things:

1. Return an object. Define a class and return an instance of that class.
2. Return a structure.
3. Return an array.
4. Use reference parameters (altough this is not returning in the purest meaning of it).

The answers you''ve received before are nice.

HTH!

大多数API函数都采用这种方式.
*返回错误值-检查出什么问题
*具有结构大小的参数，用于版本检查
*参数带有标志(位域)以标记有效成员

Most API functions do it in this way.
* return with error value - to check whats wrong
* parameter with struct size for version checking
* parameter with flags (bitfield) to mark the valid members

typedef enum
{
  RESULTOK,
  INVALIDPARAM,
  BUFFERTOOSMALL,
  // and so on

} MYERRORS;

typedef struct
{
  unsigned int  cbStruct; // ==sizeof(VARIABLE_RESULT_LIST)
  enum
  {
    VALUE1 = 1<<0,
    VALUE2 = 1<<1,
    VALUE3 = 1<<2,
    RESULT = 1<<2,
  };
  unsigned int  fValdMask;
  
  unsigned int  uiValue1;
  short          sValue2;
  TCHAR*        lpValue3;
  unsigned int  ccValue3;

  unsigned int  uiAnyResult;

} VARIABLE_RESULT_LIST;

MYERRORS MyVariableFunction(VARIABLE_RESULT_LIST* pVar)
{
  if(!pVar)
    return INVALIDPARAM;
  if(sizeof(VARIABLE_RESULT_LIST)>pVar->cbStruct)
    return BUFFERTOOSMALL;

  if(VARIABLE_RESULT_LIST::VALUE1 & pVar->fValdMask)
  {
    pVar->uiAnyResult = 42 + pVar->uiValue1;
    pVar->fValdMask |= VARIABLE_RESULT_LIST::RESULT;
  }
  else
  {
    pVar->fValdMask &= ~VARIABLE_RESULT_LIST::RESULT;
  }
  
  if(VARIABLE_RESULT_LIST::VALUE3 & pVar->fValdMask)
  {
    if(pVar->lpValue3 && (_tcslen(__T("Hello world"))<pVar->ccValue3))
      _tcscpy_s(pVar->lpValue3,pVar->ccValue3,__T("Hello world"));
    else // buffer too small
      pVar->fValdMask &= ~VARIABLE_RESULT_LIST::VALUE3;
  }

  // ignored in this version
  pVar->fValdMask &= ~VARIABLE_RESULT_LIST::VALUE2;

  return RESULTOK;
}

void main()
{
  VARIABLE_RESULT_LIST  var = { sizeof(VARIABLE_RESULT_LIST), };
  TCHAR                  str[256];
  
  var.fValdMask = 0;

  var.uiValue1  = 23;
    var.fValdMask |= VARIABLE_RESULT_LIST::VALUE1;

  var.lpValue3  = str;
  var.ccValue3  = sizeof(str)/sizeof(str[0]);
    var.fValdMask |= VARIABLE_RESULT_LIST::VALUE3;
    
  if(RESULTOK==MyVariableFunction(&var))
  {
    if(VARIABLE_RESULT_LIST::VALUE1 & var.fValdMask)
      _tprintf(__T("uiValue1: %i\r\n"),var.uiValue1);
    if(VARIABLE_RESULT_LIST::VALUE2 & var.fValdMask)
      _tprintf(__T("sValue2: %i\r\n"),(int)var.sValue2);
    if(VARIABLE_RESULT_LIST::VALUE3 & var.fValdMask)
      _tprintf(__T("lpValue3: %s\r\n"),var.lpValue3);
  }
}

问候.

这篇关于从函数返回两个值的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！