将枚举指针传递给函数

Question

我正在尝试将一个在函数之外声明的枚举传递给一个函数，以便更改函数内部的枚举值会更改指向的枚举值。在对象范围内仅使用枚举本身不是一个选项，因为我希望将此函数与多个不同的枚举实例一起使用。

我有一个名为'ColourState'的枚举。如下所示进行声明。和一个指向ColourState的指针。

enum ColourState {COLOUR1, COLOUR2};
ColourState* CS_GO_score;

指针是这样初始化的。

CS_GO_score = new ColourState;
*CS_GO_score = ColourState::COLOUR2;

我现在正在尝试将CSS_GO_score指向的ColourState传递给函数'pulsateColour'

就像这样。

void HUD::pulsateColour(GLfloat *colour1, GLfloat *colour2, GLfloat *objectCol, ColourState goingTo, int timeInFrames)
{
    GLfloat difference[4];
    //give us an array of values to change the array by in the alloted time
    difference[0] = (colour1[0]-colour2[0])/timeInFrames;
    difference[1] = (colour1[1]-colour2[1])/timeInFrames;
    difference[2] = (colour1[2]-colour2[2])/timeInFrames;
    difference[3] = (colour1[3]-colour2[3])/timeInFrames;

    //depending on the state, transform the array in one direction or another

    if(goingTo == ColourState::COLOUR2)//if we're moving toward colour 2
    {
        for(int i = 0; i<4; i++)
        {
        objectCol[i] -= difference[i];//subract the difference till we get there
        //we need to SNAP to the colour as we will not hit it every time using floats
            if( (objectCol[i]>(colour2[i]-(difference[i]*2))) && (objectCol[i]<(colour2[i]+(difference[i]*2)))  )
            {//if we hit this tiny but huuuge target
                objectCol[i] = colour2[i];//SNAP
            }

        }
    }else{
        if(goingTo == ColourState::COLOUR1)
        {
            for(int i = 0; i<4; i++)
            {
                objectCol[i] += difference[i];//add the difference till we get there
                //we need to SNAP to the colour as we will not hit it every time using floats
            if( (objectCol[i]>(colour1[i]-(difference[i]*2))) || (objectCol[i]<(colour1[i]+(difference[i]*2)))  )
            {//if we hit this tiny but huuuge target
                objectCol[i] = colour1[i];//SNAP
            }

            }
        }
    }

    if((objectCol[0] == colour1[0])&&(objectCol[1] == colour1[1])&&(objectCol[2] == colour1[2])&&(objectCol[3] == colour1[3]))
    {//if the objcolour == colour 1
        goingTo = ColourState::COLOUR2;//it's now time to move towards colour 2
    }else{
        if((objectCol[0] == colour2[0])&&(objectCol[1] == colour2[1])&&(objectCol[2] == colour2[2])&&(objectCol[3] == colour2[3]))
        {//if the objcolour == colour 2
            goingTo = ColourState::COLOUR1;//it's now time to move towards colour1  
        }

    }
}

这个函数的调用方式如下。

pulsateColour(white,blue, GO_scoreColour, *CS_GO_score, 10);

然而，当'goingTo'和'CS_GO_score'指针的值（它们应该是相同的地址，因此在技术上是相同的对象，对吧？）被观察时，在VS监视器中只看到了被'goingTo'指向的值（因为它是函数本地变量）发生了改变。我做错了什么？

- Guy Joel McLean

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所以你是一个反恐精英玩家；）谢谢你的问题，那对我很有帮助！ - Alexandre Rozier

Answer 1

你正在以值的方式传递枚举，因此该函数会拥有您传递的任何内容的本地副本。如果您想传递一个枚举并修改它的值，则建议按引用传递。

enum ColourState {COLOUR1, COLOUR2};

void change_colour(ColourState& c)
{
  c = COLOUR2;
}

....

ColourState cs = COLOUR1;
change_colour(cs);

- juanchopanza

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再一次，互联网的智者们为我提供了帮助。谢谢！ - Guy Joel McLean

Answer 2

然而，当指向'goingTo'和'CS_GO_score'的值的指针（它们应该是相同的地址，因此在技术上是相同的对象，对吗？）

不是这样的... 如果您传递指针本身，则它将是“相同的对象”。在这里，您正在传递指针指向的值。或者，您可能希望传递引用。

void HUD::pulsateColour(GLfloat *colour1, 
                        GLfloat *colour2, 
                        GLfloat *objectCol, 
                        ColourState goingTo, /* pass by value */
                        int timeInFrames)

...

我正在尝试将一个在函数范围外声明的枚举传递给一个函数，以便在函数内改变枚举的值会改变指向的枚举的值。您需要更改函数以接受指针或引用：

  ColourState *goingTo, /* pass direct the pointer */

或者

  ColourState &goingTo, /* pass a reference-dont need to change the body of the function */

- qPCR4vir

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我尝试传递指针本身，同时更改函数以接受指针而不是值。然而，在函数内部，我被告知赋值和布尔运算符（=和==）不能用于更改或比较值。例如，'*CS_GO_score == ColourState::COLOUR_2'。然而，通过引用传递已经起作用了。谢谢。 - Guy Joel McLean

当函数接收到 ColourState goingTo 时，goingTo == ColourState::COLOUR_2 是一个错误吗？ - qPCR4vir