你可以把它的工作,通过使用不同的后盾变量,当合成它看起来像这样:@synthesize nicestArrayEver = nicestArrayEverSubClass_;
#import <Foundation/Foundation.h>
@interface CustomClass : NSObject
@property (nonatomic, strong) NSArray * nicestArrayEver;
@end
@implementation CustomClass
@synthesize nicestArrayEver ;
-(id)init
{
if (self = [super init]) {
nicestArrayEver = [[NSArray alloc] init];
}
return self;
}
@end
@interface ASubClassCustomClass : CustomClass
@property (nonatomic, strong) NSMutableArray * nicestArrayEver;
@end
@implementation ASubClassCustomClass
@synthesize nicestArrayEver = nicestArrayEverSubClass_;
-(id)init{
if (self = [super init]) {
nicestArrayEverSubClass_ = [[NSMutableArray alloc] init];
}
return self;
}
@end
int main(int argc, const char * argv[])
{
@autoreleasepool {
CustomClass *c1 = [[[CustomClass alloc] init] autorelease];
ASubClassCustomClass *c2 = [[[ASubClassCustomClass alloc] init] autorelease];
NSLog(@"%@", NSStringFromClass([[c1 nicestArrayEver] class]));
NSLog(@"%@", NSStringFromClass([[c2 nicestArrayEver] class]));
}
return 0;
}
输出
2012-05-27 01:59:16.221 NicestArray[2312:403] __NSArrayI
2012-05-27 01:59:16.225 NicestArray[2312:403] __NSArrayM
另一种方法可能是有基类中有两个初始化方法,一个是实例化属性,另一个是不会的,但是将该任务留给子c lass - 这会阻止你创造昂贵的物品,只是为了扔掉它们。
现在基类可以直接使用第二个初始化实例化,并进入错误状态。您可以通过使用isMemberOfClass:
检查自身类型来避免这种情况,并且如果类类型是基类,则会引发错误。
@interface CustomClass : NSObject
@property (nonatomic, strong) NSArray * nicestArrayEver;
-(id)initWithoutArray;
@end
@implementation CustomClass
@synthesize nicestArrayEver ;
-(id) initWithoutArray
{
if (self = [super init]) {
if ([self isMemberOfClass:[CustomClass class]]) {
[NSException raise:@"AbstractMethodCall" format:@"%@ should be called only from Subclasses of %@", NSStringFromSelector(_cmd), NSStringFromClass([self class])];
}
}
return self;
}
-(id)init
{
if (self = [super init]) {
nicestArrayEver = [[NSArray alloc] init];
}
return self;
}
@end
@interface ASubClassCustomClass : CustomClass
@property (nonatomic, strong) NSMutableArray * nicestArrayEver;
@end
@implementation ASubClassCustomClass
@synthesize nicestArrayEver = nicestArrayEverSubClass_;
-(id)init{
if (self = [super initWithoutArray]) {
nicestArrayEverSubClass_ = [[NSMutableArray alloc] init];
}
return self;
}
@end
int main(int argc, const char * argv[])
{
@autoreleasepool {
CustomClass *c1 = [[[CustomClass alloc] init] autorelease];
ASubClassCustomClass *c2 = [[[ASubClassCustomClass alloc] init] autorelease];
NSLog(@"%@", NSStringFromClass([[c1 nicestArrayEver] class]));
NSLog(@"%@", NSStringFromClass([[c2 nicestArrayEver] class]));
//this works, as it is the subclass
ASubClassCustomClass *shouldWork = [[[ASubClassCustomClass alloc] init] autorelease];
// ouch!
CustomClass *shouldCrash = [[[CustomClass alloc] initWithoutArray] autorelease];
}
return 0;
}
+1用于回答问题并轻易证明我错了。 :) –