[英]Passing a function as a parameter to a method in C++
I want to make a method for a (mathematical) matrix class to process objects with the function given in parameter, but I'm stuck with function pointers! 我想为一个(数学)矩阵类创建一个方法,用参数中给出的函数处理对象,但是我坚持使用函数指针!
My code: 我的代码:
#include <iostream>
class Matrix{
public:
Matrix(int,int);
~Matrix();
int getHeight();
int getWidth();
float getItem(int,int);
void setItem(float,int,int);
float getDeterminans(Matrix *);
void applyProcessOnAll(float (*)());
private:
int rows;
int cols;
float **MatrixData;
};
Matrix::Matrix(int width, int height){
rows = width;
cols = height;
MatrixData = new float*[rows];
for (int i = 0;i <= rows-1; i++){
MatrixData[i] = new float[cols];
}
}
Matrix::~Matrix(){}
int Matrix::getWidth(){
return rows;
}
int Matrix::getHeight(){
return cols;
}
float Matrix::getItem(int sor, int oszlop){
return MatrixData[sor-1][oszlop-1];
}
void Matrix::setItem(float ertek, int sor, int oszlop){
MatrixData[sor-1][oszlop-1] = ertek;
}
void Matrix::applyProcessOnAll(float (*g)()){
MatrixData[9][9]=g(); //test
}
float addOne(float num){ //test
return num+1;
}
int main(void){
using namespace std;
cout << "starting...\r\n";
Matrix A = Matrix(10,10);
A.setItem(3.141,10,10);
A.applyProcessOnAll(addOne(3));
cout << A.getItem(10,10);
cout << "\r\n";
return 0;
}
The compiler gives me this error: error: no matching function for call to 'Matrix::applyProcessOnAll(float)' note: candidate is: note: void Matrix::applyProcessOnAll(float ( )()) note: no known conversion for argument 1 from 'float' to 'float ( )()' 编译器给我这个错误:错误:没有匹配函数调用'Matrix :: applyProcessOnAll(float)'注意:候选者是:注意:void Matrix :: applyProcessOnAll(float( )())注意:参数没有已知的转换1从'float'到'float( )()'
Thanks for the help! 谢谢您的帮助!
Now it works! 现在它有效! Thanks!
谢谢!
void Matrix::applyProcessOnAll(float (*proc)(float)){
for(int i = 0; i <= rows-1;i++)
for(int j = 0; j <= cols-1;j++)
MatrixData[i][j]=proc(MatrixData[i][j]);
}
and in main: 在主要:
A.applyProcessOnAll(*addOne);
Because your float (*g)()
does not take an argument and your addOne
takes a float
argument. 因为你的
float (*g)()
不接受参数,你的addOne
接受一个float
参数。 Change your function pointer to float (*g)(float)
and now it should work. 将函数指针更改为
float (*g)(float)
,现在它应该可以工作。
Also you should assign the function to the pointer, and not call it. 您还应该将函数分配给指针,而不是调用它。
A.applyProcessOnAll(&addOne, 3); //add args argument to `applyProcessOnAll` so you can call `g(arg)` inside.
You have two problems. 你有两个问题。
The first is the one pointed out by Tony The Lion : you specified that the function shouldn't take any parameters but you're using a function that takes a single parameter. 第一个是托尼狮子指出的那个 :你指定该函数不应该采用任何参数,但你使用的函数只需要一个参数。
The second is that you're calling applyProcessOnAll
with the results of a function call, not a pointer to the function. 第二个是你使用函数调用的结果调用
applyProcessOnAll
,而不是指向函数的指针。
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