Question

所以我试图在应用程序中使用if语句来计算人体重指数（BMI）。我需要用户能够输入公制或英制单位的重量和高度，我真的希望能够让用户输入公制重量，例如英制高度。我认为使用if语句是最好的，我的代码在下面。目前我对if语句有警告，它只是忽略它们。非常感谢任何帮助。

- (IBAction)calculateProcess:(id)sender {
    float cm = [_cmHeight.text floatValue];
    float feet = [_feetHeight.text floatValue];
    float inches = [_inchesHeight.text floatValue];
    float kg = [_kgWeight.text floatValue];
    float stone = [_stoneWeight.text floatValue];
    float pound = [_poundWeight.text floatValue];
    float height;
    float mass;

    if (cm == 0){
        float height = 0.3048*feet + 0.0254*inches;
    } else {
        float height = cm/100;
    }

    if (kg == 0){
        float mass = (6.35029*stone) + (0.453592*pound);
    } else {
        float mass = cm/100;
    }

    float bmi = mass/(height*height);
    [_resultLabel setText:[NSString stringWithFormat:@"%.2f", bmi]];
}

Answer 1

if-else块重新声明堆栈变量height和mass，因此if-else块之后的代码将看不到条件结果。改变这种方式......

// ...
float height;
float mass;

if (cm == 0){
    // see - no float type
    height = 0.3048*feet + 0.0254*inches;
} else {
    height = cm/100;
}

if (kg == 0){
    mass = (6.35029*stone) + (0.453592*pound);
} else {
    mass = cm/100;
}

顺便说一下，这两个陈述可以更加简洁：

height = (cm == 0)? 0.3048*feet + 0.0254*inches : cm/100;
mass = (kg == 0)? (6.35029*stone) + (0.453592*pound) :  cm/100;

iOS Objective C使用if语句编写Xcode

1 个答案: