objective-c - 在 Objective-C 中，如何将属性作为参数传递给函数，然后调用 setter/getter 方法？

Question

代码可能是查看我正在尝试做的事情的最佳方式:

AcInfo.h:

@interface AcInfo : NSManagedObject {
@private
}
@property (nonatomic, retain) NSString *registrationNumber;
@end

AcInfo.m:

@implementation AcInfo
    @dynamic registrationNumber;
@end

另一个类.h:

@interface AnotherClass : NSObject {
}
@property (nonatomic, retain) AcInfo               *detailItem;
@property (nonatomic, retain) IBOutlet UITextField *registrationNumberTextField;

- (void)setDetailItemValueFromUIElement:(id *)uiElement forAcInfoTarget:(id *)acInfoTarget;
@end

另一个类.m:

@import "AcInfo.h"

@implementation AnotherClass
@synthesize detailItem, registrationNumberTextField;

- (void)viewDidLoad
{
    [super viewDidLoad];

    registrationNumberTextField.text = @"Test";
    // I expect this to set detailItem.registrationNumber to the value of
    // registrationNumberTextField.text (Test) but it doesn't change anything!
    setDetailItemValueFromUIElement:registrationNumberTextField forAcInfoTarget:detailItem.registrationNumber;
}

- (void)setDetailItemValueFromUIElement:(id *)uiElement forAcInfoTarget:(id *)acInfoTarget
{   
    if ([(id)uiElement isKindOfClass:[UITextField class]]) {
        // This doesn't do anything when it returns!
        (NSString *)acInfoTarget = (UITextField *)uiElement.text
        return;
    }
}

@end

简而言之，我希望acInfoTarget调用中的getter[detailObject registrationNumber]和setter[detailObject setRegistrationNumber] setDetailItemValueFromUIElement: 函数...

Answer 1

您可以使用

按名称设置或读取属性

// setter
NSString *propertyName = @"myProperty";
[object setValue:newValue forKey:propertyName];

// getter
id value = [object valueForKey:propertyName];

不过，这比使用普通的点符号要慢，而且它经常(尽管不总是)是代码设计不当的标志。

另请注意，id 是 指针类型，因此您实际上可能不是指“(id*)”。

我认为你的代码看起来像这样:

- (void)setDetailItemValueFromUIElement:(id)uiElement forAcInfoTarget:(NSString*)acInfoTarget {
    if ([(id)uiElement isKindOfClass:[UITextField class]]) {
        NSString *newValue = ((UITextField*)uiElement).text;
        [self.detailItem setValue:newValue forKey:acInfoTarget];
    }
}