CODEWITHSUNDEEP
objective-cnsnumber
C0D3LIC1OU5
C0D3LIC1OU5

Reputation: 8680

Round NSNumber to a specific number of significant digits

Let's say I have an NSNumber object that holds a value 0.12345. All I want is an NSNumber object with a same value, but rounded to a specified number of significant digits, say 2, so value looks like this: 0.12.

Is there an obvious way to do it that I am missing?

Upvotes: 3

Views: 676

Answers (2)

GeneCode
GeneCode

Reputation: 7588

Another hacky way is:

  1. Convert your number to round after multiplied it by 100.

int yourNum = 0.12345 * 100; yourNum now is 12.

  1. Then whenever you need the number just divide by 100.

float yourNumF = yourNum / 100.0;

Not a fan of this method myself but it fits your requirement. :D

Upvotes: -1

idz
idz

Reputation: 12988

It's pretty much impossible to do it and maintain all your constraints. NSNumber has no rounding methods, so you're going to have to convert to something else. The obvious route is to convert to a double and multiply, round and divide, but you say you would prefer not to do that. So that leaves this route:

NSNumber *round(NSNumber *number, NSInteger places, NSRoundingMode mode) {
    NSDecimal d = number.decimalValue;
    NSDecimal rd;
    NSDecimalRound(&rd, &d, places, mode);
    return [NSDecimalNumber decimalNumberWithDecimal:rd];
}

Upvotes: 3

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