objective-c - 在类类别中使用 ObjC 类扩展的变量

Question

我声明了一个向其添加变量的类扩展接口。是否可以访问该类的类别中的这些变量？

Answer 1

当然 - 任何变量都可以通过运行时访问，即使它在@interface:

一些类.h

@interface SomeClass : NSObject {
    int integerIvar;
}

// methods

@end

SomeClass.m

@interface SomeClass() {
   id idVar;
}

@end

@implementation SomeClass

// methods

@end

SomeClass+Category.m

@implementation SomeClass(Category)

-(void) doSomething {
    // notice that we use KVC here, instead of trying to get the ivar ourselves. 
    // This has the advantage of auto-boxing the result, at the cost of some performance.
    // If you'd like to be able to use regex for the query, you should check out this answer:
    // http://stackoverflow.com/a/12047015/427309  
    static NSString *varName = @"idVar"; // change this to the name of the variable you need

    id theIvar = [self valueForKey:varName]; 

    // if you want to set the ivar, then do this:
    [self setValue:theIvar forKey:varName];
}

@end

您还可以使用 KVC 在 UIKit 或类似中获取类的 iVar，同时比纯运行时黑客更容易使用。