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基础知识
Double的精度为十五个十进制有效数字,
Float的精度为六个十进制有效数字。
两者都需要扩展后实现保留几位有效小数的操作,扩展方法需要在classViewController外层增加。
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代码:
import UIKit
class ViewController: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
let n1 : Float = 32.141592654
let n2 : Double = 3.141592654
print(n1)
print(n2)
print(n2.format(".3"))
// Do any additional setup after loading the view, typically from a nib. }
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
}
//扩展
extension Double {
func format(f : String) -> String {
return NSString.init(format: "%\(f)f", self) as String
}
}