dynamic string format with NSString stringWithFormat
ios, objective-c, stringwithformat
Solution
There's a better way to do this.
... stringWithFormat:@"Hour: %0*i", length, hour]; // note the asterisk
where `length` is the number of digits you want. Use `1` to get no leading zeros, use `2` to get a length of 2 with leading zeros as needed.
FYI - to solve what you originally tried you need to do it in two steps:
NSString *dynFmt = [NSString stringWithFormat:@"Hour: %%%@i", padding];
NSString *res = [NSString stringWithFormat:dynFmt, hour];
Problem
I've been trying to make a dynamic string format so that through user options precision or padding could be somewhat user defined. An example includes, the padding of leading zeros as in the 24hour time format. In normal time format, the hours can be represented by a single digit, or a digit padded by a zero. This is represented in the string format: ``` ...stringWithFormat:@"Hour: %02i", hour // leading zero padded ``` and ``` ...stringWithFormat:@"Hour: %i", hour // not leading zero padded ``` What I would like to achieve is to have a variable containing either `@""` or `@"02"` and have that variable presented in the format string between the `%` and the `i`. I have done a couple of experiments and just can't seem to do this and am beginning to think that it's not possible with `stringWithFormat`. I've tried: `...stringWithFormat:@"Hour: %%@i", padding, hour` `...stringWithFormat:@"Hour: %@%i", padding, hour` and others. Any ideas?