Question

我不确定如何解释这一点，但我很肯定有办法做到这一点，但我还没有得到它。这是我的例子：我有10个变量（整数值），并且使用变量的值，设置一个字符串。

以下是天气和云层的示例，以确定天气状况：

        if (hour1cloud <= 5) {
            hour1weather = @"Clear";
        }
        if (5 < hour1cloud <= 25) {
            hour1weather = @"Mostly Clear";
        }
        if (25 < hour1cloud <= 50) {
            hour1weather = @"Partly Cloudy";
        }
        if (50 < hour1cloud <= 83) {
            hour1weather = @"Mostly Cloudy";
        }
        if (83 < hour1cloud <= 105) {
            hour1weather = @"Overcast";
        }

假设我有hour2cloud，hour3cloud，hour4cloud等，它们与hour2weather，hour3weather等相反。有没有办法我可以制作一个通用方法，我只需输入hour1cloud并检索hour1weather？

Answer 1

你当然可以这样做：

static NSString *stringForCloudiness(int cloudiness) {
    static int const kCloudinesses[] = { 5, 25, 50, 83, 105 };
    static NSString *const kStrings[] = { @"Clear", @"Mostly Clear", @"Partly Cloudy", @"Mostly Cloudy", @"Overcast" };
    static int const kCount = sizeof kCloudinesses / sizeof *kCloudinesses;
    for (int i = 0; i < kCount; ++i) {
        if (cloudiness <= kCloudinesses[i]) {
            return kStrings[i];
        }
    }
    return @"A cloudiness level unparalleled in the history of recorded weather";
}

这有点复杂但确保您不要忘记保持阵列同步：

static NSString *stringForCloudiness(int cloudiness) {
    typedef struct {
        int cloudiness;
        __unsafe_unretained NSString *string;
    } CloudStringAssociation;

    static CloudStringAssociation const kAssociations[] = {
        { 5, @"Clear" },
        { 25, @"Mostly Clear" },
        { 50, @"Partly Cloudy" },
        { 83, @"Mostly Cloudy" },
        { 105, @"Overcast" },
        { INT_MAX, @"A cloudiness level unparalleled in the history of recorded weather" }
    };

    int i = 0;
    while (cloudiness > kAssociations[i].cloudiness) {
        ++i;
    }
    return kAssociations[i].string;
}

Answer 2

为什么不写这样的方法：

- (NSString*)weatherStringFromCloud:(int)cloud {
    NSString *weather;
    if (cloud <= 5) {
        weather = @"Clear";
    } else if (cloud <= 25) {
        weather = @"Mostly Clear";
    } else if (cloud <= 50) {
        weather = @"Partly Cloudy";
    } else if (cloud <= 83) {
        weather = @"Mostly Cloudy";
    } else if (cloud <= 105) {
        weather = @"Overcast";
    } else {
        weather = nil;
    }
    return weather;
}

然后使用各种值调用它：

hour1weather = [self weatherStringFromCloud:hour1cloud];
hour2weather = [self weatherStringFromCloud:hour2cloud];
hour3weather = [self weatherStringFromCloud:hour3cloud];
hour4weather = [self weatherStringFromCloud:hour4cloud];

如何用不同的变量重复一个动作？

2 个答案: