ios - 通过创建 NSDictionary 优化功能

Question

我正在尝试像这样优化返回 NSMutableDictionary 的函数:

 -(NSMutableDictionary *)getValuses{

    NSNumber *n1 = [NSNumber numberWithInt:-1];
    NSNumber *n2 = [NSNumber numberWithInt:-1];
    NSNumber *n3 = [NSNumber numberWithInt:-1];
    NSNumber *n4 = [NSNumber numberWithInt:-1];
    NSNumber *n5 = [NSNumber numberWithInt:-1];

    if (self.k1)
        n1 = self.k1;
    if (self.k2)
        n2 = self.k2;
    if (self.k3)
        n3 = self.k3;
    if (self.k4)
        n4 = self.k4;
    if (self.k5)
        n5 = self.k5;

    NSMutableDictionary * dictionary = [[NSMutableDictionary alloc]initWithObjectsAndKeys:n1,[NSNumber numberWithInt:2],n2,[NSNumber numberWithInt:3],n3,[NSNumber numberWithInt:4],n4,[NSNumber numberWithInt:5],n5,[NSNumber numberWithInt:6], nil];

    return dictionary;
}  

我在循环中运行这个函数超过 100 万次，所以任何优化都是好的。它可以工作，但我希望它工作得更快。

Answer 1

你真的需要 -1 值的字典吗？你可以避免所有“if/then”的东西(我听说它对于 cpu 来说可能很慢)如果你只是这样做

    NSMutableDictionary * dictionary = [[NSMutableDictionary alloc]initWithObjectsAndKeys:k1,[NSNumber numberWithInt:2],k2,[NSNumber numberWithInt:3],k3,[NSNumber numberWithInt:4],k4,[NSNumber numberWithInt:5],k5,[NSNumber numberWithInt:6], nil];
    // then you can do things like this
    id obj = [dictionary objectForKey:@2];
    if (obj)
        NSLog(@"dict with good values");
    else
        NSLog(@"old dict with -1");