想要對(duì)部分URL字符串進(jìn)行百分號(hào)編碼，請(qǐng)使用NSString的stringByAddingPercentEncodingWithAllowedCharacters:方法，給URL組件或子組件傳遞合適的字符集：

• User: URLUserAllowedCharacterSet
• Password: URLPasswordAllowedCharacterSet
• Host: URLHostAllowedCharacterSet
• Path: URLPathAllowedCharacterSet
• Fragment（片段）: URLFragmentAllowedCharacterSet
• Query（查詢(xún)）: URLQueryAllowedCharacterSet

重要：不要使用stringByAddingPercentEncodingWithAllowedCharacters:來(lái)編碼整個(gè)URL字符串，因?yàn)槊總€(gè)URL組件或子組件對(duì)于有效字符都有不同的規(guī)則。

例如，想要對(duì)包含在URL片段中的UTF-8字符串進(jìn)行百分號(hào)編碼，請(qǐng)執(zhí)行如下操作：

NSString *originalString = @"color-#708090";

NSCharacterSet *allowedCharacters = [NSCharacterSet URLFragmentAllowedCharacterSet];

NSString *percentEncodedString = [originalString stringByAddingPercentEncodingWithAllowedCharacters:allowedCharacters];

NSLog(@"%@", percentEncodedString"); // prints "color-%23708090"

let originalString = "color-#708090"

let allowedCharacters = NSCharacterSet.urlFragmentAllowed

let encodedString = originalString.addingPercentEncoding(withAllowedCharacters: allowedCharacters)

print(encodedString!) // prints "color-%23708090"

如果你想對(duì)URL組件進(jìn)行百分號(hào)編碼，使用NSURLComponents把URL分拆成它的組成部分，并訪問(wèn)相關(guān)的屬性。

例如，想要得到URL片段百分號(hào)編碼的UTF-8字符串值，請(qǐng)執(zhí)行以下操作：

NSURL *URL = [NSURL URLWithString:@"https://example.com/#color-%23708090"];

NSURLComponents *components = [NSURLComponents componentsWithURL:URL resolvingAgainstBaseURL:NO];

NSString *fragment = components.fragment;

NSLog(@"%@", fragment); // prints "color-#708090"

let url = URL(string: "https://example.com/#color-%23708090")!

let components = URLComponents(url: url, resolvingAgainstBaseURL: true)!

let fragment = components.fragment!

print(fragment) // prints "color-#708090"