iosswiftdoublerounding

Round Issue in swift

I have this Info.

let params2: [String: AnyObject] = [
    "app_token": myapptoken,
    "member_access_token": accessToken!,
    "pay_process": 0,
    "payamount_credit": 9.87 //hardcode
]

When print params2

The result is

["app_token": myapptoken, "member_access_token": accessToken, "payamount_credit": 9.869999999999999, "pay_process": 0]

The "payamount_credit": 9.87 now is "payamount_credit": 9.869999999999999

I have tried all the ways that exist round but behaves the same.

NSString(format: "%.\2f", 9.87)

Double(round(1000*9.87)/1000)

The strangest thing of all is that only happens with this specific number (9.87), is something mystical.

Playground Screen.

enter image description here

Solution

  • The problem lies within the numeric precision, simply put, some numbers cannot be defined as a Double without losing precision.

    Instead you should use NSDecimalNumber:

    let num = NSDecimalNumber(string: "9.87")