Question

虽然我可以在创建sf :: RectangleShape对象时访问成员.setPosition，但我似乎无法访问不同范围内的.setPosition成员。救命？我是Xcode的新手，但对C ++很熟悉，不知道为什么会导致错误。

class ShapeVisual : public sf::Drawable, public sf::Transformable {
public:
    int fillShape[16];
    int shapeWidth;
    int shapeHeight;

    sf::RectangleShape shapeBlock;
    float shapeBlockWidth;

    ShapeVisual() {
        shapeWidth = 4; shapeHeight = 4;

        Tetrominos::SetShape("T", &fillShape);

        shapeBlockWidth = 10.0;

        shapeBlock = sf::RectangleShape();
        shapeBlock.setPosition(0,0);
        shapeBlock.setOutlineColor(sf::Color::Green);
        shapeBlock.setSize(sf::Vector2f(shapeBlockWidth,shapeBlockWidth));
        shapeBlock.setFillColor(sf::Color(255,100,100));

    }


    virtual void draw(sf::RenderTarget& target, sf::RenderStates states) const {
        states.transform *= getTransform();

        for (int Bx = 0; Bx < this->shapeWidth; Bx++) {
        for (int By = 0; By < this->shapeHeight; By++) {
            shapeBlock.setPosition(Bx*shapeBlockWidth, By*shapeBlockWidth);
            //ERROR HERE: No matching member call for shapeBlock.setPosition.

            if (fillShape[Bx + By*shapeWidth] != 0) {
                target.draw(shapeBlock,states);
            }
        } }

    }
};

错误的确切文字是

/Volumes/Minerva/Users/dustinfreeman/Documents/Shapeshifter/Code/Shapeshifter/shapeshifter/shapeshifter/shapes.cpp:147:20: error: no matching member function for call to 'setPosition'
        shapeBlock.setPosition(Bx*shapeBlockWidth, By*shapeBlockWidth);
       ~~~~~~~~~~~^~~~~~~~~~~


/usr/local/include/SFML/Graphics/Transformable.hpp:70:10: note: candidate function not viable: no known conversion from 'const sf::RectangleShape' to 'sf::Transformable' for object argument
void setPosition(float x, float y);
     ^


/usr/local/include/SFML/Graphics/Transformable.hpp:84:10: note: candidate function not viable: requires single argument 'position', but 2 arguments were provided
void setPosition(const Vector2f& position);
     ^

以下是sf :: RectangleShape类的文档：http://www.sfml-dev.org/documentation/2.0/classsf_1_1RectangleShape.php

编辑：我将shapeBlock更改为指针，现在它似乎编译并运行正常。但我找不到原始代码的问题。

Answer 1

您的draw功能为const。这意味着您无法修改对象的属性。 C ++只允许您在属性上调用其他const成员函数。在这种情况下，setPosition不是const成员函数，因此无法编译。

当你切换到一个指针时，你必须做其他事情才能使它工作，显然。

成员函数的可访问性似乎随SFML，C ++和Xcode的范围而变化

1 个答案: