是否有可能以不同的精度呈现相同的变量?
例如,如果我要呈现两个整数的加法,则结果如下:
result = 2+3;
NSLog(@"%.0f", result);
但是如果有一个除法,它会像:
result = 2/3;
NSLog(@"%.1f", result);
虽然呈现 π (pi),但它会像:
result = M_PI;
NSLog(@"%.19f", result); //And it would be 3.141592653589793238
最佳答案
NSNumber
将为你做一些快速而肮脏的格式化,
NSNumber * five = [NSNumber numberWithDouble:3+2];
NSNumber * twoThirds = [NSNumber numberWithDouble:2/3.0];
NSNumber * mPi = [NSNumber numberWithDouble:M_PI];
NSLog(@"%@", [five stringValue]);
NSLog(@"%@", [twoThirds stringValue]);
NSLog(@"%@", [mPi stringValue]);
2011-11-17 21:52:12.621 Precision[13359:903] 5
2011-11-17 21:52:12.624 Precision[13359:903] 0.6666666666666666
2011-11-17 21:52:12.625 Precision[13359:903] 3.141592653589793
但是你真的应该使用NSNumberFormatter
:
NSNumberFormatter * formatter = [[NSNumberFormatter alloc] init];
[formatter setUsesSignificantDigits:YES];
NSLog(@"%@", [formatter stringFromNumber:five]);
NSLog(@"%@", [formatter stringFromNumber:twoThirds]);
[formatter setMaximumSignificantDigits:16];
NSLog(@"%@", [formatter stringFromNumber:mPi]);
2011-11-17 21:52:12.629 Precision[13359:903] 5
2011-11-17 21:52:12.630 Precision[13359:903] 0.666667
2011-11-17 21:52:12.630 Precision[13359:903] 3.14159265358979
string format specifiers还允许可变精度;使用星号代替小数点后的数字:
int precision = 3;
NSLog(@"%.*f", precision, 2/3.0);
关于objective-c - 仅在需要时提供精确的数字 - 这可能吗?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/8174735/