xcode 如何将类型 double 转换为字符串 iPhone？
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How to convert type double to string iPhone?
提问by Dietrich Epp
I am calculating the velocity of an iPhone, and I need to know how to convert the variable calculatedSpeed which is type double to type string to display on a label.
我正在计算 iPhone 的速度，我需要知道如何将 double 类型的变量 calculateSpeed 转换为类型字符串以显示在标签上。
Here is what I have in the header:
这是我在标题中的内容：
@interface myProject : UIViewController <CLLocationManagerDelegate> {
double calculatedSpeed;
UILabel *velocityLabel;
}
And here is what I have in the main:
这是我的主要内容：
-(void)speedLocation:(CLLocationManager *)manager didUpdateToLocation:(CLLocation *)newLocation fromLocation:(CLLocation *)oldLocation
{
double gpsSpeed = newLocation.speed;
if(oldLocation != nil)
{
CLLocationDistance distanceChange = [newLocation getDistanceFrom:oldLocation];
NSTimeInterval sinceLastUpdate = [newLocation.timestamp timeIntervalSinceDate:oldLocation.timestamp];
calculatedSpeed = distanceChange / sinceLastUpdate;
velocityLabel.text = calculatedSpeed;
}
}
Notice how I am trying to set velocityLabel to calculatedSpeed, which is a variable with the type double. So it naturally gives me the error: incompatible type for argument 1 of 'setText:'.
请注意我如何尝试将velocityLabel 设置为calculatedSpeed，这是一个double 类型的变量。所以它自然给了我错误：'setText:' 的参数 1 的类型不兼容。
Your help is greatly appreciated.
非常感谢您的帮助。
Thanks!
谢谢！
回答by Dietrich Epp
velocityLabel.text = [NSString stringWithFormat:@"%g", calculatedSpeed];
