Replace text within specific part of NSString

Question

Is it possible to change text within a specific part of an NSString? For example, I want to use stringByReplacingOccurrencesOfString, but only within a certain part of a string. In this example, I only want to replace #'s after #q=, and before &lang=en-us. Like this:

Initial string: https://google.com/search#q=hello#&lang=en-us

What it should be replaced with: https://google.com/search#q=hello%23&lang=en-us

What using stringByReplacingOccurrencesOfString returns if I tell it to replace #'s with %23: https://google.com/search%23q=hello%23&lang=en-us

Thanks for your help!

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– NP Rooski Z, Commented Sep 26, 2016 at 3:07

CRD · Accepted Answer · 2016-09-24 11:16:44Z

3

The direct answer to your question is yes, you can use stringByReplacingOccurrencesOfString:withString:options:range:; the range parameter specifies the part of the string within which replacements should be done.

There are other searching methods provide by NSString which may help you determine a suitable value for range.

Having said the above your approach is probably rather "fragile" - prone to break easily as input data changes - and maybe you should consider the string as what it is, a URL, and either construct it with appropriate escaping in the first place; or parse it into its parts, add the escaping, and then reassemble. There are methods on NSURL and NSString which help you do that.

HTH

edited Sep 24, 2016 at 11:16

answered Sep 24, 2016 at 10:10

CRD

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NP Rooski Z · Accepted Answer · 2016-09-24 07:12:52Z

0

Seems like you want to URL encode existing string

NSString *input = @"https://google.com/search#q=hello%23&lang=en-us";
NSURL *url = @"https://google.com/search#q=hello%23&lang=en-us";
NSString *params = [url parameterString];
NSString *enc = [params stringByAddingPercentEscapesUsingEncoding:
 NSUTF8StringEncoding];
//append URLs host+path with enc

No error checking is done in above code, it only gives idea

edited Sep 24, 2016 at 7:12

answered Sep 23, 2016 at 22:54

NP Rooski Z

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1 Comment

jwuki Over a year ago

Thanks for your response! The problem with this solution is that using this outputs the string with the hashtags and percent signs changed to the correct UTF8 encoding, but it does it for the entire string, not just within the #q= part.

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