Question

I have a long string I want to retrieve from a URL and store at app launch. Later, I want to insert individual values into that string.

I’d like to do something like this:

NSString *numberLine = @"1 %@ 3 %@ 5 %@";

//... (later) ...

NSString *final = [NSString stringWithFormat:numberLine, @"two", @"four", @"six"]; 

NSLog(@"%@", final); //Should output "1 two 3 four 5 six"

I want the @"two" to be inserted into the placeholder %@ that was earlier saved into numberLine.

Is there a good way to accomplish something like this?

So far my only thought is to do something like:

NSString *script = @"width = PLACEHOLDERpx";
script = [script stringByReplacingOccurrencesOfString:@"PLACEHOLDER" withString:@"12"];

Answer 1

What you are describing is a template. You want to leave placeholders in a string that will be filled out with data. While you could use %@ and %d through a string that gets difficult as the string grows more complex. You may want to use a template library like Mustache for Objective-C. This will let you write expressions like this:

Hello {{SomeVariable}}

All you have to do is pass in an NSDictionary with keys that correspond to the data you want to render. So for the example above you might do the following:

NSString *result = [GRMustacheTemplate renderObject:[NSDictionary dictionaryWithObject:@"World" forKey:@"SomeVariable"];
                                         fromString:@"Hello {{SomeVariable}}"
                                              error:NULL];

This will produce a result string Hello World.