核心数据瞬态计算属性

Question

我有一个包含lastName和firstName属性的实体.由于超出此问题范围的原因,我想要一个fullName属性,该属性被计算为firstName + space + lastName的串联.

因为这纯粹是一个计算值,不需要重做/撤消或任何其他更复杂的瞬态属性(合并等),我的直觉告诉我只需覆盖getter方法返回所述计算值.阅读建议,如果我这样做,我唯一关心的是它是否符合KVO,我可以通过使用keyPathsForValuesAffectingVolume解决这个问题,以确保更改firstName或lastName触发通知,以便观察fullName.

我错过了什么吗？我正在检查,因为我是这个环境的初学者.

Answer 1

我对此也很陌生，所以我不完全确定我的答案，但据我了解，你是对的。

- (NSString *)fullName
{
    [self willAccessValueForKey:@"fullName"];
    NSString *tmp = [self primitiveFullName];
    [self didAccessValueForKey:@"fullName"];

    if (!tmp) {
        tmp = [NSString stringWithFormat:@"%@ %@", [self firstName], [self lastName]];
        [self setPrimitiveFullName:tmp];
    }
    return tmp;
}

- (void)setFirstName:(NSString *)aFirstName
{
    [self willChangeValueForKey:@"firstName"];
    [self setPrimitiveFirstName:aFirstName];
    [self didChangeValueForKey:@"firstName"];

    [self setPrimitiveFullName:nil];
}

- (void)setLastName:(NSString *)aLastName
{
    [self willChangeValueForKey:@"lastName"];
    [self setPrimitiveLastName:aLastName];
    [self didChangeValueForKey:@"lastName"];

    [self setPrimitiveFullName:nil];
}

+ (NSSet *)keyPathsForValuesAffectingFullName
{
    return [NSSet setWithObjects:@"firstName", @"lastName", nil];
}