在類別類中使用ObjC類擴展的變量

Question

我聲明瞭一個類擴展接口，它添加了變量。是否可以訪問該類別中的那些變量？

Answer 1

當然 - 任何變量是通過運行時可以訪問，即使是不可見的@interface：

SomeClass.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 

您也可以使用KVC得到了UIKit框架或類似的高德班，同時更易於比純運行時，黑客使用。