本文介绍了Objective C NSString *属性保留计数奇数的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
我有以下示例类：
Test.h：
@interface Test : UIButton {
NSString *value;
}
- (id)initWithValue:(NSString *)newValue;
@property(copy) NSString *value;
Test.m：
@implementation Test
@synthesize value;
- (id)initWithValue:(NSString *)newValue {
[super init];
NSLog(@"before nil value has retain count of %d", [value retainCount]);
value = nil;
NSLog(@"on nil value has retain count of %d", [value retainCount]);
value = newValue;
NSLog(@"after init value has retain count of %d", [value retainCount]);
return self;
}
产生以下输出：
2008-12-31 09:31:41.755 Concentration[18604:20b] before nil value has retain count of 0
2008-12-31 09:31:41.756 Concentration[18604:20b] on nil value has retain count of 0
2008-12-31 09:31:41.757 Concentration[18604:20b] after init value has retain count of 2147483647
我这样调用：
Test *test = [[Test alloc] initWithValue:@"some text"];
应该值的保留计数为1吗？我缺少什么？
Shouldn't value have a retain count of 1? What am I missing?
感谢您的帮助。
推荐答案
引用一个不可变的字符串。赋值不需要复制值（字符串数据），因为它是不可变的。如果你做一个可变操作，例如value = [newValue uppercaseString]，那么它应该将位复制到值，值的保留计数增加。
You've got a reference to an immutable string. Assignment doesn't need to copy the value (the string data) since it's immutable. If you do a mutable operation, like value = [newValue uppercaseString] then it should copy the bits into value, and value's retain count incremented.
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