My app crashes when trying to get a String containing special characters - objective-c

Question

when i try to display a String, my application crashes:
NSLog(#"The start point is: %#",startPt);
This is the startPt value: 39-49%20Avenue%20d'Ivry,%2075013%20Paris,%20France. Actually it's returned from the Google Maps web service.
Sometimes, the application didn't crashes, but i got something weird in the Log:
The start point is: text/javascript
Why i am not able to assign the String 39-49%20Avenue%20d'Ivry,%2075013%20Paris,%20France to a NSString variable?
EDIT:
Here is the JSON response parsing:
NSString *responseString=[request responseString];
NSDictionary *responseDict=[responseString JSONValue];
NSArray *resultsArray = [responseDict objectForKey:#"results"];
location=[[resultsArray valueForKey:#"formatted_address"] objectAtIndex:0];
location=[location stringByAddingPercentEscapesUsingEncoding:NSASCIIStringEncoding];
NSLog(#"The location is : %#",location);//39-49%20Avenue%20d'Ivry,%2075013%20Paris,%20France
And this is the JSON response returned from the Google maps API:
{
"results" : [
{
"address_components" : [
{
"long_name" : "39-49",
"short_name" : "39-49",
"types" : [ "street_number" ]
},
{
"long_name" : "Avenue d'Ivry",
"short_name" : "Avenue d'Ivry",
"types" : [ "route" ]
},
{
"long_name" : "Quartier de la Gare",
"short_name" : "Quartier de la Gare",
"types" : [ "neighborhood", "political" ]
},
{
"long_name" : "13th arrondissement of Paris",
"short_name" : "13th arrondissement of Paris",
"types" : [ "sublocality", "political" ]
},
{
"long_name" : "Paris",
"short_name" : "Paris",
"types" : [ "locality", "political" ]
},
{
"long_name" : "Paris",
"short_name" : "75",
"types" : [ "administrative_area_level_2", "political" ]
},
{
"long_name" : "Île-de-France",
"short_name" : "IdF",
"types" : [ "administrative_area_level_1", "political" ]
},
{
"long_name" : "France",
"short_name" : "FR",
"types" : [ "country", "political" ]
},
{
"long_name" : "75013",
"short_name" : "75013",
"types" : [ "postal_code" ]
}
],
"formatted_address" : "39-49 Avenue d'Ivry, 75013 Paris, France",
"geometry" : {
"bounds" : {
"northeast" : {
"lat" : 48.82332110,
"lng" : 2.36638740
},
"southwest" : {
"lat" : 48.82296810,
"lng" : 2.36571090
}
},
"location" : {
"lat" : 48.82313960,
"lng" : 2.36602210
},
"location_type" : "RANGE_INTERPOLATED",
"viewport" : {
"northeast" : {
"lat" : 48.82449358029150,
"lng" : 2.367398130291502
},
"southwest" : {
"lat" : 48.82179561970850,
"lng" : 2.364700169708498
}
}
},
"types" : [ "street_address" ]
},
{
"address_components" : [
{
"long_name" : "Quartier de la Gare",
"short_name" : "Quartier de la Gare",
"types" : [ "neighborhood", "political" ]
},
{
"long_name" : "13th arrondissement of Paris",
"short_name" : "13th arrondissement of Paris",
"types" : [ "sublocality", "political" ]
},
{
"long_name" : "Paris",
"short_name" : "Paris",
"types" : [ "locality", "political" ]
},
{
"long_name" : "Paris",
"short_name" : "75",
"types" : [ "administrative_area_level_2", "political" ]
},
{
"long_name" : "Île-de-France",
"short_name" : "IdF",
"types" : [ "administrative_area_level_1", "political" ]
},
{
"long_name" : "France",
"short_name" : "FR",
"types" : [ "country", "political" ]
}
],
"formatted_address" : "Quartier de la Gare, Paris, France",
"geometry" : {
"bounds" : {
"northeast" : {
"lat" : 48.83810700000001,
"lng" : 2.3869610
},
"southwest" : {
"lat" : 48.8189240,
"lng" : 2.3556050
}
},
"location" : {
"lat" : 48.82807520,
"lng" : 2.36740680
},
"location_type" : "APPROXIMATE",
"viewport" : {
"northeast" : {
"lat" : 48.83810700000001,
"lng" : 2.3869610
},
"southwest" : {
"lat" : 48.8189240,
"lng" : 2.3556050
}
}
},
"types" : [ "neighborhood", "political" ]
},
{
"address_components" : [
{
"long_name" : "13th arrondissement of Paris",
"short_name" : "13th arrondissement of Paris",
"types" : [ "sublocality", "political" ]
},
{
"long_name" : "Paris",
"short_name" : "Paris",
"types" : [ "locality", "political" ]
},
{
"long_name" : "Paris",
"short_name" : "75",
"types" : [ "administrative_area_level_2", "political" ]
},
{
"long_name" : "Île-de-France",
"short_name" : "IdF",
"types" : [ "administrative_area_level_1", "political" ]
},
{
"long_name" : "France",
"short_name" : "FR",
"types" : [ "country", "political" ]
}
],
"formatted_address" : "13th arrondissement of Paris, Paris, France",
"geometry" : {
"bounds" : {
"northeast" : {
"lat" : 48.84496499999999,
"lng" : 2.3900530
},
"southwest" : {
"lat" : 48.8155730,
"lng" : 2.3411080
}
},
"location" : {
"lat" : 48.83222220,
"lng" : 2.35555560
},
"location_type" : "APPROXIMATE",
"viewport" : {
"northeast" : {
"lat" : 48.84496499999999,
"lng" : 2.3900530
},
"southwest" : {
"lat" : 48.8155730,
"lng" : 2.3411080
}
}
},
"types" : [ "sublocality", "political" ]
},
{
"address_components" : [
{
"long_name" : "75013",
"short_name" : "75013",
"types" : [ "postal_code" ]
},
{
"long_name" : "Paris",
"short_name" : "Paris",
"types" : [ "locality", "political" ]
},
{
"long_name" : "Paris",
"short_name" : "75",
"types" : [ "administrative_area_level_2", "political" ]
},
{
"long_name" : "Île-de-France",
"short_name" : "IdF",
"types" : [ "administrative_area_level_1", "political" ]
},
{
"long_name" : "France",
"short_name" : "FR",
"types" : [ "country", "political" ]
}
],
"formatted_address" : "75013 Paris, France",
"geometry" : {
"bounds" : {
"northeast" : {
"lat" : 48.84493089999999,
"lng" : 2.39026440
},
"southwest" : {
"lat" : 48.81587960,
"lng" : 2.34112720
}
},
"location" : {
"lat" : 48.8307590,
"lng" : 2.3592040
},
"location_type" : "APPROXIMATE",
"viewport" : {
"northeast" : {
"lat" : 48.84493089999999,
"lng" : 2.39026440
},
"southwest" : {
"lat" : 48.81587960,
"lng" : 2.34112720
}
}
},
"types" : [ "postal_code" ]
},
{
"address_components" : [
{
"long_name" : "Paris",
"short_name" : "Paris",
"types" : [ "locality", "political" ]
},
{
"long_name" : "Paris",
"short_name" : "75",
"types" : [ "administrative_area_level_2", "political" ]
},
{
"long_name" : "Île-de-France",
"short_name" : "IdF",
"types" : [ "administrative_area_level_1", "political" ]
},
{
"long_name" : "France",
"short_name" : "FR",
"types" : [ "country", "political" ]
}
],
"formatted_address" : "Paris, France",
"geometry" : {
"bounds" : {
"northeast" : {
"lat" : 48.9021450,
"lng" : 2.46992090
},
"southwest" : {
"lat" : 48.8155730,
"lng" : 2.2241990
}
},
"location" : {
"lat" : 48.8566140,
"lng" : 2.35222190
},
"location_type" : "APPROXIMATE",
"viewport" : {
"northeast" : {
"lat" : 48.9021450,
"lng" : 2.46992090
},
"southwest" : {
"lat" : 48.8155730,
"lng" : 2.2241990
}
}
},
"types" : [ "locality", "political" ]
},
{
"address_components" : [
{
"long_name" : "Paris",
"short_name" : "75",
"types" : [ "administrative_area_level_2", "political" ]
},
{
"long_name" : "Île-de-France",
"short_name" : "IdF",
"types" : [ "administrative_area_level_1", "political" ]
},
{
"long_name" : "France",
"short_name" : "FR",
"types" : [ "country", "political" ]
}
],
"formatted_address" : "Paris, France",
"geometry" : {
"bounds" : {
"northeast" : {
"lat" : 48.9021450,
"lng" : 2.46992090
},
"southwest" : {
"lat" : 48.8155730,
"lng" : 2.2241990
}
},
"location" : {
"lat" : 48.87633370,
"lng" : 2.34612070
},
"location_type" : "APPROXIMATE",
"viewport" : {
"northeast" : {
"lat" : 48.9021450,
"lng" : 2.46992090
},
"southwest" : {
"lat" : 48.8155730,
"lng" : 2.2241990
}
}
},
"types" : [ "administrative_area_level_2", "political" ]
},
{
"address_components" : [
{
"long_name" : "Île-de-France",
"short_name" : "IdF",
"types" : [ "administrative_area_level_1", "political" ]
},
{
"long_name" : "France",
"short_name" : "FR",
"types" : [ "country", "political" ]
}
],
"formatted_address" : "Île-de-France, France",
"geometry" : {
"bounds" : {
"northeast" : {
"lat" : 49.2415040,
"lng" : 3.5590070
},
"southwest" : {
"lat" : 48.1200810,
"lng" : 1.446170
}
},
"location" : {
"lat" : 48.84991980,
"lng" : 2.63704110
},
"location_type" : "APPROXIMATE",
"viewport" : {
"northeast" : {
"lat" : 49.2415040,
"lng" : 3.5590070
},
"southwest" : {
"lat" : 48.1200810,
"lng" : 1.446170
}
}
},
"types" : [ "administrative_area_level_1", "political" ]
},
{
"address_components" : [
{
"long_name" : "France",
"short_name" : "FR",
"types" : [ "country", "political" ]
}
],
"formatted_address" : "France",
"geometry" : {
"bounds" : {
"northeast" : {
"lat" : 51.08896180,
"lng" : 9.559956999999999
},
"southwest" : {
"lat" : 41.34232760,
"lng" : -5.1412280
}
},
"location" : {
"lat" : 46.2276380,
"lng" : 2.2137490
},
"location_type" : "APPROXIMATE",
"viewport" : {
"northeast" : {
"lat" : 51.08896180,
"lng" : 9.559956999999999
},
"southwest" : {
"lat" : 41.34232760,
"lng" : -5.1412280
}
}
},
"types" : [ "country", "political" ]
}
],
"status" : "OK"
}

Answer 1

I can think of two possibilities :
(1) Why do you assume the string is ASCII? Try a different encoding :
location = [location stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
Perhaps Google are using a unicode ' instead of one within the ASCII set? And if you're looking at address data then you can be fairly sure that odd characters are going to get put in there!
and (2) (this one is more unlikely given you have posted the JSON in your question but worth thinking about)
When you first get location you aren't checking that it's actually a string (you aren't checking that 'formatted_address' is an array either!)
What if the JSON returned was this (say there is a bug in the server?) :
{
...
"formatted_address" : [ { } ]
...
}
Here, [[resultsArray valueForKey:#"formatted_address"] objectAtIndex:0]; would work, but it wouldn't return an NSString.
Try adding in this kind of check :
location=[[resultsArray valueForKey:#"formatted_address"] objectAtIndex:0];
if (NO == [location isKindOfClass:[NSString class]]) {
NSLog(#"Location wasn't a string (%#) : %#", [location class], location);
} else {
location=[location stringByAddingPercentEscapesUsingEncoding:NSASCIIStringEncoding];
NSLog(#"The location is : %#",location);//39-49%20Avenue%20d'Ivry,%2075013%20Paris,%20France
}

Answer 2

My guess is that startPt isn't an NSString, but rather a char*. If that's the case, the simplest way to create an NSString from it is with [NSString stringWithFormat:#"%s", startPt].