成员没有默认构造函数

Question

我是openFrameworks/C++的新手,但已经使用Processing/Java一段时间了.我无法实例化我在testApp头中创建的类的对象.

它抛出错误:

Implicit default constructor for 'testApp' must explicitly initialize the member 'currentSeq' which does not have a default constructor.

这是我的Sequence.h文件:

#pragma once
#include "ofMain.h"

class Sequence{

public:
    Sequence(long _start, long _stop){
        start = _start;
        stop = _stop;
    }

    long start;
    long stop;

};

这是我的testApp.h:

#pragma once

#include "ofMain.h"
#include "sequence.h"

class testApp : public ofBaseApp{
    public:

        void setSequences();
        bool needsNewSeq();

        void setup();
        void update();
        void draw();

        void keyPressed(int key);
        void keyReleased(int key);
        void mouseMoved(int x, int y);
        void mouseDragged(int x, int y, int button);
        void mousePressed(int x, int y, int button);
        void mouseReleased(int x, int y, int button);
        void windowResized(int w, int h);
        void dragEvent(ofDragInfo dragInfo);
        void gotMessage(ofMessage msg);

        int numSequences;
        int seqIndex;
        bool isPaused;

        Sequence currentSeq;
        vector <Sequence> sequences;
        ofVideoPlayer myVideo;

};

问题是currentSeq变量.由于某些原因,序列的矢量很好.根据这个 openFrameworks教程,我似乎正在做正确的事情.

Answer 1

您的parameritized构造函数Sequence(long, long)会覆盖编译器生成的默认构造函数,从而隐式删除默认构造函数testApp.在你做的行:

Sequence currentSeq;

这会抑制默认构造testApp,因为没有可行的构造函数currentSeq,因此错误.要解决此问题,请为您的Sequence类应用默认构造函数(您还应该将start和stop成员初始化为0):

class Sequence
{
public:
    Sequence() : start(0), stop(0)
//  ^^^^^^^^^^ ^^^^^^^^^^^^^^^^^^^
    { }

    Sequence(long _start, long _stop)
        : start(_start), stop(_stop) // Use member-initializer list here too
    { }

    long start;
    long stop;

};

或者,您可以为此提供默认构造函数testApp并构造currentSeq如下:

class testApp : public ofBaseApp
{
    testApp() : currentSeq(0, 0)
    { }
    // ...
};