[英]how do i initialize a public variable in a public class method
我有一個公共類,我在其中創建了一個數組,該數組從構造函數中獲取其大小,並且需要在其他函數中使用(包括 int main)。 因此變量必須是公開的。 我的代碼看起來像這樣:
class myclass {
public:
int parameter1;
int parameter2;
myclass(int p, int p2) {
parameter1 = p;
parameter2 = p2;
}
void makeArray() {
int array[parameter1][parameter2]; //I want this array to be public as the next method needs access to it
}
void otherFunction() {
array[1][2] = 5; //just an example of what i need to do
}
}
查看如何使用指針和動態內存..
做你想做的事情是這樣的:
class myclass {
public:
int parameter1;
int parameter2;
int **a;
myclass(int p, int p2) {
parameter1 = p;
parameter2 = p2;
a = nullptr;
}
~myclass() {
// TODO: delete "a"
}
void makeArray() {
// TODO: delete "a" if it has already been allocated
a = new *int[parameter1];
for (int i = 0; i < parameter1; ++i) {
a[i] = new int[parameter2];
}
}
void otherFunction() {
// TODO: check that "a" has already been allocated
a[1][2] = 5; //just an example of what i need to do
}
}
您還可以在構造函數中分配數組,因為您已經傳入了必要的信息。
這是做同樣事情的更優化的方法:
class myclass {
public:
int parameter1;
int parameter2;
int *array;
myclass(int p1, int p2) {
parameter1 = p1;
parameter2 = p2;
}
void makeArray() {
array = new int[parameter1*parameter2];
}
void otherFunction() {
// ary[i][j] is then rewritten as ary[i*sizeY+j]
array[1*parameter2+2] = 5;
}
};
int main()
{
int sizeX = 5;
int sizeY = 5;
myclass m1(sizeX,sizeY);
m1.makeArray();
m1.otherFunction();
cout << m1.array[1*sizeY+2] << endl;
return 0;
}
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