ios - Q : how to refactor repeating if block code with properties as much as possible?

Question

我想尽可能将以下具有属性访问权限的重复代码压缩到 for 循环或使用函数中:

    if (sender == self.section1SegmentedControl) {
        switch (sender.selectedSegmentIndex) {
            case 0: //YES
                self.DSProtokoll.section1YesNo = TRUE;
                break;
            case 1: //NO
                self.DSProtokoll.section1YesNo = FALSE;
                break;
        }
    }
    if (sender == self.section2SegmentedControl) {
        switch (sender.selectedSegmentIndex) {
            case 0: //YES
                self.DSProtokoll.section2YesNo = TRUE;
                break;
            case 1: //NO
                self.DSProtokoll.section2YesNo = FALSE;
                break;
        }
    }
    if (sender == self.section3SegmentedControl) {
        switch (sender.selectedSegmentIndex) {
            case 0: //YES
                self.DSProtokoll.section3YesNo = TRUE;
                break;
            case 1: //NO
                self.DSProtokoll.section3YesNo = FALSE;
                break;
        }
    }

我试着把它放在一个函数中:

- (void)processYesNoIfMatch:(UISegmentedControl *)sender source:(UISegmentedControl *) a dest:(BOOL *) b {
    if (sender == a) {
        switch (sender.selectedSegmentIndex) {
            case 0: //YES
                *b = TRUE;
                break;
            case 1: //NO
                *b = FALSE;
                break;
        }
    }
}

但我无法使用该函数并使用不同的参数多次调用它:

[self processYesNoIfMatch:sender source:self.section1SegmentedControl dest:&self.DSProtokoll.section1YesNo];
[self processYesNoIfMatch:sender source:self.section2SegmentedControl dest:&self.DSProtokoll.section2YesNo];

因为不允许使用指向属性的指针

Address of property expression requested

在objective-c中如何用函数或for循环尽可能地简化这种重复的原始代码？

Answer 1

Objective-C 方法调用使用动态绑定(bind)，如果您乐于用一些编译时检查来换取可能的运行时错误，您可以大大缩短代码。将以下内容视为伪代码(因为它已直接输入到答案中并且只是代码片段):

for(int controlNumber = 1; controlNumber <= MAX_CONTROL_NUMBER; controlNumber++)
{
   // construct the property name as a *string*
   NSString *controlProperty = [NSString stringWithFormat:@"section%dSegmentedControl", controlNumber);
   // get the property value - if the property does not exist this is a runtime error
   NSSegmentedControl *controlN = [self valueForKey:controlProperty];
   if (sender == controlN)
   {
      // construct the property path as a *string*
      NSString *yesNoProperty = [NSString stringWithFormat:@"DSProtokoll.section%dYesNo", controlNumber;
      // set the property value, must pass the BOOL as an NSNumber object
      [self setValue:@(sender.selectedSegmentIndex == 0) forKeyPath:yesNoProperty];
      // all done, exit loop
      break;
   }
}

还有其他方法可以解决这个问题。您的特定尝试失败只是因为您试图获取一个属性的地址，就好像它是一个变量；属性是一对函数，一个getter和setter，你可以获取这些函数的地址，并将它们传递给其他函数来调用。然而，您可能会发现传递一个设置属性的 block 比传递一个指向属性 setter 的函数指针更容易。通过这样的更改，您的 processYesNoIfMatch 方法将起作用。

HTH