iOS Swift如何在NSURL中使用包含％2的字符串？

Question

I am very new to to using web services and coding in general. So please let me know if i am not making any sense.

I am using two methods to construct an url to use to call the flickr API. Everything works well, the only thing i can't make work is using the "%2Curl_m" parameter in my url. When the url gets constructed "%2Curl_m" becomes "%252Curl_m".

I've tried google and searching here but i didn't find an answer. The only thing that came close is that it might have to do with string encoding. I've looked in the documentation but i really couldn't make much sense out of it.

I am using this two methods to construct the url:

private class func flickrURL(method method: Method, page:Int,
    parameters: [String:String]?) -> NSURL {
        let components = NSURLComponents(string: baseURLString)!
        var queryItems = [NSURLQueryItem]()

        let baseParams = [
            "method": method.rawValue,
            "format": "json",
            "nojsoncallback": "1",
            "api_key": APIKey,
            "text": "car",
            "per_page": "50",
            "page": String(page)
        ]

        for (key, value) in baseParams {
            let item = NSURLQueryItem(name: key, value: value)
            queryItems.append(item)
        }

        if let additionalParams = parameters {
            for (key, value) in additionalParams {
                let item = NSURLQueryItem(name: key, value: value)
                queryItems.append(item)
            }
        }

        components.queryItems = queryItems
    print(components.URL!)

        return components.URL!
}


private static var nextPage = 0
class func recentPhotosURL() -> NSURL {
    nextPage += 1
    print(nextPage)
    let curl = "%2Curl_m"
    print(curl)
    return flickrURL(method: .RecentPhotos, page: nextPage,
        parameters: ["extras": "\(curl),url_h,date_taken"])
}

The url I get is:

https://api.flickr.com/services/rest?page=2&text=car&api_key=XXXXXXXXXXXXXXXXXXX&method=flickr.photos.search&per_page=50&format=json&nojsoncallback=1&extras=%252Curl_m,url_h,date_taken

The url I need is:

https://api.flickr.com/services/rest?page=2&text=car&api_key=XXXXXXXXXXXXXXXXXXX&method=flickr.photos.search&per_page=50&format=json&nojsoncallback=1&extras=%2Curl_m,url_h,date_taken

Answer 1

These 3 lines:

let curl = "%2Curl_m"
print(curl)
return flickrURL(method: .RecentPhotos, page: nextPage, parameters: ["extras": "\(curl),url_h,date_taken"])

A quick look at the Flickr API tells me that it's not a valid value in the extras parameter, that would be url_m .

%2C is the percent-encoded form for comma ( , ). NSURLQueryItem thinks you mean the string %2C so it encodes the % sign to become %25 . That's how you get %252Curl_m .

I don't know where you picked up the %2C . Did use a web utility and included the comma by mistake?

Answer 2

When your URL is translated into a String, some characters are escaped like % translates to %25 and so…
You can get the non-escaped string with stringByRemovingPercentEncoding .

print("%252".stringByRemovingPercentEncoding!) // prints "%2"