使用NSObject方法 – (id)awakeAfterUsingCoder：(NSCoder *)解码器作为示例,文档说：
Allows an object,after being decoded,to substitute another object
for itself. For example,an object that represents a font might,upon
being decoded,release itself and return an existing object having the
same font description as itself. In this way,redundant objects can be
eliminated.
通常你会这样做
[self release]; return substitutedObject;
使用ARC,你必须离开这条线.这不会泄漏吗？或者我应该只相信NSCoder对象为我发布原始对象？如果是这样,为什么你必须首先用非ARC代码明确释放自己？
根据编译器文档中关于self的内容,我认为self = nil是不正确的：http://clang.llvm.org/docs/AutomaticReferenceCounting.html#misc.self
解决方法
如上所述,你不能写[self release];.另外,awakeAfterUsingCoder：不是初始化者 – 你可能不会重新分配自己.
Wouldn’t this leak?
是.在下面的程序中证明.
Or should I just trust the NSCoder object to release the original object for me?
没有.
下面是一种避免泄漏的方法 – 我不会称之为“新模式”,这只是我想到的第一种方法.它涉及自我的显式释放,在这种情况下显式保留结果：
#import <Foundation/Foundation.h>
@interface MONBoolean : NSObject < NSCoding >
- (id)initWithBool:(bool)pBool;
- (bool)isTrue;
- (bool)isFalse;
@end
static NSString * const MONBoolean_KEY_value = @"MONBoolean_KEY_value";
@implementation MONBoolean
{
bool value;
}
- (id)initWithBool:(bool)pBool
{
self = [super init];
if (0 != self) {
value = pBool;
}
return self;
}
- (bool)isTrue
{
return true == value;
}
- (bool)isFalse
{
return false == value;
}
- (NSString *)description
{
return [[NSString alloc] initWithFormat:@"<%s:%p> : %s",object_getClassName(self),self,self.isTrue ? "true" : "false"];
}
- (void)encodeWithCoder:(NSCoder *)aCoder
{
[aCoder encodeBool:value forKey:MONBoolean_KEY_value];
}
- (id)initWithCoder:(NSCoder *)aDecoder
{
self = [super init];
if (0 != self) {
value = [aDecoder decodeBoolForKey:MONBoolean_KEY_value];
}
return self;
}
- (id)awakeAfterUsingCoder:(NSCoder *)aDecoder
{
const bool b = value;
// cannot reassign self outside of an initializer.
// if not released,will result in a leak:
CFRelease((__bridge const void*)self);
MONBoolean * result = [[MONBoolean alloc] initWithBool:b];
// now we have to retain explicitly because this is
// an autoreleasing method:
CFRetain((__bridge const void*)result);
return result;
}
@end
int main(int argc,const char * argv[])
{
@autoreleasepool {
MONBoolean * a = [[MONBoolean alloc] initWithBool:true];
NSData * data = [NSKeyedArchiver archivedDataWithRootObject:a];
MONBoolean * b = [NSKeyedUnarchiver unarchiveObjectWithData:data];
NSLog(@"%@",b);
}
system("leaks NAME_OF_PROCESS_HERE");
return 0;
}
