Question

I am currently trying to put together an URL where I specify some GET parameters. But I want to use japanese or other characters too in this URL.

Is there a way to convert a NSString to a string containing the HTML entities for the ‘special’ characters in my NSString?

I am currently using the following code, which seems to work, except for ‘special characters’ like chinese and japanese:

NSString* url = @'/translate_a/t?client=t&sl=auto&tl='; url = [url stringByAppendingString:destinationLanguage]; url = [url stringByAppendingString:@'&text=']; url = [url stringByAppendingString:text];  NSURL* nsurl = [[NSURL alloc] initWithScheme:@'http' host:@'translate.google.com' path:url];   NSError* error; NSString* returnValue = [[NSString alloc] initWithContentsOfURL:nsurl encoding:NSUTF8StringEncoding error:&error]; 

Answer 1

To properly URL encode your parameters, you need to convert each name and value to UTF-8, then URL encode each name and value separately, then join names with values using ‘=’ and name-value pairs using ‘&’.

I generally find it easier to put all the parameters in an NSDictionary, then build the query string from the dictionary. Here’s a category that I use for doing that:

// file NSDictionary+UrlEncoding.h #import <Cocoa/Cocoa.h>  @interface NSDictionary (UrlEncoding)  -(NSString*) urlEncodedString;  @end   // file NSDictionary+UrlEncoding.m #import 'NSDictionary+UrlEncoding.h'  // private helper function to convert any object to its string representation static NSString *toString(id object) {   return [NSString stringWithFormat: @'%@', object]; }  // private helper function to convert string to UTF-8 and URL encode it static NSString *urlEncode(id object) {   NSString *string = toString(object);   return [string stringByAddingPercentEscapesUsingEncoding: NSUTF8StringEncoding]; }   @implementation NSDictionary (UrlEncoding)  -(NSString*) urlEncodedString {   NSMutableArray *parts = [NSMutableArray array];   for (id key in self) {     id value = [self objectForKey: key];     NSString *part = [NSString stringWithFormat: @'%@=%@',                       urlEncode(key), urlEncode(value)];     [parts addObject: part];   }   return [parts componentsJoinedByString: @'&']; }  @end 

The method build an array of name-value pairs called parts by URL encoding each key and value, then joining them together with ‘=’. Then the parts in the parts array are joined together with ‘&’ characters.

So for your example:

#import 'NSDictionary+UrlEncoding.h' // ... NSMutableDictionary *parameters = [NSMutableDictionary dictionary]; [parameters setValue: @'t' forKey: @'client']; [parameters setValue: @'auto' forKey: @'sl']; [parameters setValue: destinationLanguage forKey: @'tl']; [parameters setValue: text forKey: @'text']; NSString *urlString = [@'/translate_a/t?' stringByAppendingString: [parameters urlEncodedString]];