[英]return reference to dynamically generated 2D array
//header file
CGPoint **positions;
//Implementation file
int rows = 10;
int columns = 6;
positions = malloc(rows * sizeof(CGPoint));
for(int i=0; i<rows; i++){
positions[i] = malloc(columns * sizeof(CGPoint));
}
positions[0][0] = CGPointMake(682, 0);
positions[0][1] = CGPointMake(682, 336);
positions[0][2] = CGPointMake(0, 0);
positions[0][3] = CGPointMake(-341, 336);
positions[0][4] = CGPointMake(0, 336);
positions[0][5] = CGPointMake(341, 0);
positions[1][0] = CGPointMake(341, 0);
positions[1][1] = CGPointMake(341, 336);
positions[1][2] = CGPointMake(682, 336);
positions[1][3] = CGPointMake(-341, 336);
positions[1][4] = CGPointMake(0, 336);
positions[1][5] = CGPointMake(0, 0);
//and so on..
我需要編寫以下函數的幫助,該函數將返回像這樣的位置的隨機第二維。 返回完整的子數組position [0]或positions [1],
- (CGPoint *)point {
return positions[arc4random() % rows];
}
CGPointMake(x, y)
在堆棧而不是堆中創建結構。
執行您想要的代碼:
unsigned int row = 10;
unsigned int column = 10;
CGPoint **points = malloc(row * sizeof(CGPoint *));
for (int r = 0; r < row; ++r) {
points[r] = malloc(column * sizeof(CGPoint));
for (int c = 0; c < column; ++c) {
points[r][c].x = 0.0;
points[r][c].y = 0.0;
}
}
警告:您必須記住在不再需要2D數組時將其釋放。 一種方法是將其包裝在Obj-C包裝器中,然后在init
和dealloc
。
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