如何在NSNumber上做数学

Question

I am trying to take a reading off a sensor and display it as a percentage. [some value] will always be between 0 and 1.

Here is my code:

NSNumber *reading = [some value];
reading = [reading floatValue] * 100;

However, I get "Assigning to NSNumber *_strong from incompatible type float"

I am new to working NSNumber objects and struggle to understand how to display my sensor reading as a percentage for the user. Ex: 75%

Thanks for any help

Answer 1

You need to box integer or float value to store it in NSNumber,

as:

NSNumber *reading = @(10.123);
reading = @([reading floatValue] * 100);

After this, you can print/convert it into string as :

NSString *display=[NSString stringWithFormat:@"%@%%",reading];

NOTE %% double percentage symbols

Answer 2

You should keep the value in float first and the need to create the NSNumber from it.

NSNumber *reading = [NSNumber numberWithFloat:someValue];
float newNum = [reading floatValue] * 100;
reading = [NSNumber numberWithFloat:newNum];

Answer 3

I dont like to write multi line code because i am a bit lazy to multiline code writing. I am always looking for compressed solutions. Please find below the following solutions.

 float testValue=5.00032;
    NSString *resultValue=[NSString stringWithFormat:@"%@%%",[NSNumber numberWithFloat:(testValue*100)]];

Above solution is for float value. If you want provide input as integer value,Please replace the "numberWithFloat" with "numberWithInt".

I hope that this solution will help you. Thanks.