如何在if语句中的条件内创建宏

Question

我需要遍历嵌套在while循环内的for循环，以获得几种不同的条件。

每个语句的代码的唯一更改是要应用的比较条件。

原来我复制粘贴所有的代码多次，并改变大于符号的方向。

例如：

if (direction.horizontal == UIScrollDirectionLeft) { 
    int column = startColumn+1; 
    while (column < maxAllowed) { 
     for (int row = minRow; row < maxRow; row++) { 
      repeated code 
     } 
     column++; 
} else { 
    int column = minColumn -1; 
    while (column >= 0) { 
     for (int row = minRow; row < maxRow; row++) { 
      repeated code 
     } 
     column--; 
    } 
} 

是否有可能做条件运算符宏以便于代码重用？

我真的很喜欢的东西可能是这样的：

int startColumn = (direction.horizontal == UIScrollDirectionLeft) ? (startColumn+1) : minColumn -1; 
SignOfOperator theSignInTheWhile = (direction.horizontal == UIScrollDirectionLeft) ? "<" : ">="; 
int conditionToTestInWhile = (direction.horizontal == UIScrollDirectionLeft) ? maxAllowed : 0; 

while(startColumn,theSignInTheWhile,conditionToTestInWhile) { 
    // repeated code 
} 

我有另外4个情况下，像上面的一个...

Answer 1

你只需要一次循环代码。只需更改步骤值和终止值。例如：

int start_column, end_column, column_step; 
    : 
switch (direction.horizontal) { 
    case UIScrollDirectionLeft: 
    column = start_column + 1; 
    column_step = 1; 
    end_column = max_allowed; 
    break; 
    case UIScrollDirectionRight: 
    column = min_column - 1; 
    column_step = -1; 
    end_column = -1; 
    break; 
    : 
} 
while (column != end_column) { 
    for (int row = minRow; row < maxRow; row++) { 
    repeated_code(); 
    } 
    column += column_step; 
}