Question

I have a UILabel that is currently displaying the value on a UISlider as a value between 0 and 1 in increments of .1 (so it would display .1 or .2 or .3 etc up to 1). However I want to display this value as a % out of 100, but I’m not quite familiar with formatting floating point numbers. Here is the code I have right now:

sliderLabel.text = [NSString stringWithFormat:@"%.1f", [[f numberFromString:thresholdFile] floatValue]];  

Answer 1

Haha, this can be tricky….
From the printf docs:

.number
For e, E and f specifiers: this is the number of digits to be printed after the decimal point.

Thus, what you really want is this:

[NSString stringWithFormat:@"%f %%", [mySlider value] * 100];

Let’s break this down, shall we?

1. %f: Prints the first floating point number in the arguments list, which is:

   [mySlider value] * 100
   

   Notice the * 100 part there, which converts a number in the range of 0 ... 1 to a range of 0 ... 100. You may wish to call round() on this if you don’t want a decimal percentage.

2. %%: Prints out an actual % character. This is because printf searches for switches that begin with the % character, and so if we had one verbatim in the string, it would throw a hissy fit. Thus, we escape that with another % (just like we would with a backslash), and it’s fine.