Urlcomponents Queryitems Losing Percent Encoding When Mutated

URLComponents queryItems losing percent encoding when mutated

You should use percentEncodedQuery if you have a query that is already percent encoded:

let startURL = "https://test.com/test.jpg"
var components = URLComponents(string: startURL)!
components.percentEncodedQuery = "X-Test-Token=FQdzEPH%2F%2F%2F"

if let compURL = components.url {
    print(compURL)
}

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Or you can specify it unescaped (and it leaves it unescaped as it's not necessary to escape / characters in a query):

let startURL = "https://test.com/test.jpg"
var components = URLComponents(string: startURL)!
components.queryItems = [URLQueryItem(name: "X-Test-Token", value: "FQdzEPH///")]

if let compURL = components.url {
    print(compURL)
}

---

And if you have to update queryItems, just make sure to set percentEncodedQuery at the very end:

let startURL = "https://test.com/test.jpg"
let encodedQuery = "X-Test-Token=FQdzEPH%2F%2F%2F"
var components = URLComponents(string: startURL)!
components.queryItems = [URLQueryItem(name: "foo", value: "bar, baz, & qux")]
if let query = components.percentEncodedQuery {
    components.percentEncodedQuery = query + "&" + encodedQuery
} else {
    components.percentEncodedQuery = encodedQuery
}

if let compURL = components.url {
    print(compURL)
}

Encode '+' using URLComponents in Swift

As pointed out in the other answers, the "+" character is valid in
a query string, this is also stated in the
query​Items documentation:

According to RFC 3986, the plus sign is a valid character within a query, and doesn't need to be percent-encoded. However, according to the W3C recommendations for URI addressing, the plus sign is reserved as shorthand notation for a space within a query string (for example, ?greeting=hello+world).

[...]

Depending on the implementation receiving this URL, you may need to preemptively percent-encode the plus sign character.

And the
W3C recommendations for URI addressing
state that

Within the query string, the plus sign is reserved as shorthand notation for a space. Therefore, real plus signs must be encoded. This method was used to make query URIs easier to pass in systems which did not allow spaces.

This can be achieved by "manually" building
the percent encoded query string, using a custom character set:

let queryParams = ["foo":"a+b", "bar": "a-b", "baz": "a b"]
var components = URLComponents()

var cs = CharacterSet.urlQueryAllowed
cs.remove("+")

components.scheme = "http"
components.host = "www.example.com"
components.path = "/somepath"
components.percentEncodedQuery = queryParams.map {
    $0.addingPercentEncoding(withAllowedCharacters: cs)!
    + "=" + $1.addingPercentEncoding(withAllowedCharacters: cs)!
}.joined(separator: "&")

let finalURL = components.url
// http://www.example.com/somepath?bar=a-b&baz=a%20b&foo=a%2Bb

Another option is to "post-encode" the plus character in the generated
percent-encoded query string:

let queryParams = ["foo":"a+b", "bar": "a-b", "baz": "a b"]
var components = URLComponents()
components.scheme = "http"
components.host = "www.example.com"
components.path = "/somepath"
components.queryItems = queryParams.map { URLQueryItem(name: $0, value: $1) }
components.percentEncodedQuery = components.percentEncodedQuery?
    .replacingOccurrences(of: "+", with: "%2B")

let finalURL = components.url
print(finalURL!)
// http://www.example.com/somepath?bar=a-b&baz=a%20b&foo=a%2Bb

iOS: Prevent URL from being percent escaped automatically?

Per the spec for URI: "A host identified by an Internet Protocol literal address, version 6 [RFC3513] or later, is distinguished by enclosing the IP literal within square brackets ("[" and "]")." rfc3986.

Thus you can't use square brackets for your purpose without escaping them. Your server's REST service is at fault for not handling the escaped characters in the query params. (And I've had situations in recent past where I've had to ask my REST team to fix this sort of problem where they forgot to support escaped query parameter values).

Swift URLComponents not converting empty spaces correctly

So the answer is that NSLog does not print out percent Escaped strings correctly, print on the other hand does. The best thing would have been just to set a breakpoint on the NSLog line and check the url value if it is correct, which it was.

How do I URL encode a string

Unfortunately, stringByAddingPercentEscapesUsingEncoding doesn't always work 100%. It encodes non-URL characters but leaves the reserved characters (like slash / and ampersand &) alone. Apparently this is a bug that Apple is aware of, but since they have not fixed it yet, I have been using this category to url-encode a string:

@implementation NSString (NSString_Extended)

- (NSString *)urlencode {
    NSMutableString *output = [NSMutableString string];
    const unsigned char *source = (const unsigned char *)[self UTF8String];
    int sourceLen = strlen((const char *)source);
    for (int i = 0; i < sourceLen; ++i) {
        const unsigned char thisChar = source[i];
        if (thisChar == ' '){
            [output appendString:@"+"];
        } else if (thisChar == '.' || thisChar == '-' || thisChar == '_' || thisChar == '~' || 
                   (thisChar >= 'a' && thisChar <= 'z') ||
                   (thisChar >= 'A' && thisChar <= 'Z') ||
                   (thisChar >= '0' && thisChar <= '9')) {
            [output appendFormat:@"%c", thisChar];
        } else {
            [output appendFormat:@"%%%02X", thisChar];
        }
    }
    return output;
}

Used like this:

NSString *urlEncodedString = [@"SOME_URL_GOES_HERE" urlencode];

// Or, with an already existing string:
NSString *someUrlString = @"someURL";
NSString *encodedUrlStr = [someUrlString urlencode];

---

This also works:

NSString *encodedString = (NSString *)CFURLCreateStringByAddingPercentEscapes(
                            NULL,
                            (CFStringRef)unencodedString,
                            NULL,
                            (CFStringRef)@"!*'();:@&=+$,/?%#[]",
                            kCFStringEncodingUTF8 );

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Some good reading about the subject:

Objective-c iPhone percent encode a string?

Objective-C and Swift URL encoding

http://cybersam.com/programming/proper-url-percent-encoding-in-ios

https://devforums.apple.com/message/15674#15674
http://simonwoodside.com/weblog/2009/4/22/how_to_really_url_encode/

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