clean way to add query string to NSString?

Question

So I have a NSString with a url like this:

NSString stringWithFormat:@"/reading.php?title=blah&description="blah"&image_url=blah... "

what is the best way to append query string to this string? is there a dictionary kind of way to do this?

Could you rephrase and be more specific with what you want?

StilesCrisis
– StilesCrisis

2012-03-20 22:48:07 +00:00
Commented Mar 20, 2012 at 22:48 — StilesCrisis
– StilesCrisis, Commented Mar 20, 2012 at 22:48

Serdar Dogruyol · Accepted Answer · 2012-03-20 23:04:57Z

2

What you want to do is this.

[NSString stringWithFormat:@"/reading.php?title=blah&description=%@&image_url=blah... ",blah];

Basically %@ in the context meaning that you'll pass use a dynamic value which will be a string.

edited Mar 20, 2012 at 23:04

answered Mar 20, 2012 at 22:51

Serdar Dogruyol

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3 Comments

adit Over a year ago

yea, but it's too long and it's not clean & pretty if I have 20 parameters in the query string

Serdar Dogruyol Over a year ago

Then you shall divide your 20 parameters into another strings and then add it into your main string.

borrrden Over a year ago

There is no "pretty" way to add 20 dynamic values to a string

Paul.s · Accepted Answer · 2012-03-21 00:10:50Z

How about a category?

This is not great but for a first pass should give you something to get started

@interface NSDictionary (ps_additions) - (NSString *)ps_URLParamsValue; @end @implementation NSDictionary (ps_additions) - (NSString *)ps_URLParamsValue; { NSMutableString *params = [NSMutableString string]; [self enumerateKeysAndObjectsUsingBlock:^(id key, id obj, BOOL *stop){ [params appendFormat:@"%@=%@&", key, obj]; }]; return [params copy]; } @end

This would end up with something like:

NSDictionary *params = [NSDictionary dictionaryWithObjectsAndKeys:@"42", @"special_number", @"value", @"another", nil]; NSString *myString = [NSString stringWithFormat:@"/reading.php?%@", [params URLParamsValue]]; NSLog(@"%@", myString); #=> 2012-03-20 23:54:55.855 Untitled[39469:707] /reading.php?another=value&special_number=42&

When done right, category methods almost always make things prettier. I agree that the dictionary category above is a good idea. I added an answer below that could easily be a string category method. One little issue on your soln here is that I think it will leave a dangling ampersand at the end of the param string.
I don't think the dangling ampersand would cause any issues as it would most likely just be ignored, but this was a first pass and would hopefully be improved if it was going to be used.

Ali Hamze · Accepted Answer · 2012-03-21 00:07:03Z

You can use something like:

NSString *parameter1 = @"blah"; NSString *parameter2 = @"anotherblah"; NSString *fullURL = [NSString stringWithFormat:@"/reading.php?title=%@&image_url=%@", parameter1, parameter2];

You can add as many parameters as you want. Use "%@" where you will be dynamically adding the text.

Good luck :)

danh · Accepted Answer · 2012-03-21 00:38:13Z

0

Copy pasting from Paul.s - which is the correct answer, imo - and fixing a (most likely inconsequential) problem of a dangling ampersand...

@interface NSDictionary (ps_additions) - (NSString *)ps_URLParamsValue; @end @implementation NSDictionary (ps_additions) - (NSString *)ps_URLParamsValue; { if (!self.count) return @""; NSMutableString *params = [NSMutableString string]; [self enumerateKeysAndObjectsUsingBlock:^(id key, id obj, BOOL *stop){ [params appendFormat:@"%@=%@&", key, obj]; }]; // return everything except that last ampersand return [[params copy] substringToIndex:[params length]-1]; }

@end

edited Mar 21, 2012 at 0:38

answered Mar 21, 2012 at 0:01

danh

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5 Comments

danh Over a year ago

As @Paul.s correctly suggests above, a category method will clean up the code a bit. You can package this one on NSString by simply removing the to:urlString parameter and appending the query string to self. Also, watch out for that special case on the last iteration - you don't need an extra "&" on the end of the query string. (though most web services might find it harmless).

Paul.s Over a year ago

You could move the lastObject call outside of the loop as it's not going to change.

danh Over a year ago

agreed. also, i'm not certain, but i bet your enumeration block is more efficient because it just walks the dictionary data structure picking the keys and values in a single pass. no hash needed (probably).

danh Over a year ago

And come to think of it, I think the dictionary category is more generally useful than the string category idea. The only value-add to string is the append. Not sure what the correct SO thing to do here is. I guess I'll up-vote your answer? or edit mine? I'll do both.

Paul.s Over a year ago

Ah now you see why I didn't bother trying to deal with the ampersand issue in a clean way, it's entirely possible that the dictionary would be empty in which case this would crash with an NSRangeException

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