blocks|key|5605435|text|这是一个苹果的bug。相反，请使用|type|unstyled|depth|inlineStyleRanges|entityRanges|data|5605436|NSString+-stringByAddingPercentEncodingWithAllowedCharacters:|code-block|syntax|javascript|5605437|使用|5605438|NSCharacterSet+%2BURLQueryAllowedCharacterSet|5605439|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

This is an Apple bug. Instead use

<pre><code>NSString -stringByAddingPercentEncodingWithAllowedCharacters:
</code></pre>

with

<pre><code>NSCharacterSet +URLQueryAllowedCharacterSet
</code></pre>

blocks|key|2366208|text|我的答案来自Radar+24076063，并解释了它为什么会这样工作(对文本进行了一些清理)：|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|2366209|2366210|+'%2B‘字符在查询组件中是合法的，因此不需要使用百分号编码。|blockquote|2366211|2366212|某些系统使用'%2B‘作为空格，并要求'%2B’加号字符采用百分号编码。然而，这种两阶段编码(将加号转换为%252B，然后将空格转换为加号)容易出错，因为它很容易导致编码问题。如果URL是规范化的，它也会中断(URL的语法规范化包括删除所有不必要的百分比编码-参见rfc3986第6.2.2.2节)。|2366213|因此，如果因为您的代码与之对话的服务器而需要该行为，那么您将自己处理额外的转换。下面是一段代码，展示了两种方法都需要做的事情：|2366214|NSURLComponents+*components+=+[NSURLComponents+alloc+]；NSArray+*items+=+[NSArray+arrayWithObjects:NSURLQueryItem+queryItemWithName:@"name“value:@"Value+%2B"，nil]；components.queryItems+=+items；NSLog(@"URL：%25@"，components+queryItems)；NSLog(@"URL：%25@"，components+string)；//将percentEncodedQuery中的所有"%2B“替换为"%252B”(百分比编码%2B)，然后将所有"%2520“(百分比编码空格)替换为"%2B”components.percentEncodedQuery+=+[components.percentEncodedQuery+stringByReplacingOccurrencesOfString:@"%2B“withString:@"%252B”stringByReplacingOccurrencesOfString:@"%2520“withString:@"%2B"]；NSLog(@"URL+string+after：%25@"，components+string)；//如果您收到具有该形式的查询的URL，并希望使用queryItems+components.percentEncodedQuery+=+[components.percentEncodedQuery+stringByReplacingOccurrencesOfString:@"%2B“withString:@"%2520”stringByReplacingOccurrencesOfString:@"%252B“withString:@"%2B"]；NSLog(@"URL+string+back：%25@"，components+string)；NSLog(@"URL+queryItems：%25@"，components+queryItems)；|2366215|输出为：|2366216|URL+queryItems：(+"+{名称=名称，值=值%2B}“)+URL字符串之前：?name=Value%2520%2B+URL字符串之后：?name=Value%2B%252B+URL字符串返回：?name=Value%2520%2B+URL+queryItems：(+"+{名称=名称，值=值%2B}”)|2366217|entityMap|0|LINK|mutability|MUTABLE|url|http://www.openradar.me/24076063^0|6|E|0|0|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|10|8|@]|9|@$A|11|B|12|1|13]]|C|$]]|$1|D|3|-4|5|6|7|14|8|@]|9|@]|C|$]]|$1|E|3|F|5|G|7|15|8|@]|9|@]|C|$]]|$1|H|3|-4|5|6|7|16|8|@]|9|@]|C|$]]|$1|I|3|J|5|6|7|17|8|@]|9|@]|C|$]]|$1|K|3|L|5|6|7|18|8|@]|9|@]|C|$]]|$1|M|3|N|5|6|7|19|8|@]|9|@]|C|$]]|$1|O|3|P|5|6|7|1A|8|@]|9|@]|C|$]]|$1|Q|3|R|5|6|7|1B|8|@]|9|@]|C|$]]|$1|S|3|-4|5|6|7|1C|8|@]|9|@]|C|$]]]|T|$U|$5|V|W|X|C|$Y|Z]]]]

My answer from <a href="http://www.openradar.me/24076063" rel="noreferrer">Radar 24076063</a> with an explanation of why it works the way it does (with a little cleanup of the text):

<blockquote>
 The '+' character is legal in the query component so it does not need to be percent-encoded.
 
 Some systems use the '+' as a space and require '+' the plus character to be percent-encoded. However, that kind of two stage encoding (converting plus sign to %2B and then converting space to plus sign) is prone to errors because it easily leads to encoding problems. It also breaks if the URL is normalized (syntax normalization of URLs includes the removal of all unnecessary percent-encoding &mdash; see rfc3986 section 6.2.2.2).
 
 So, if you need that behavior because of the server your code is talking to, you'll handle the extra transformation(s) yourself. Here's a snippet of code that shows what you need to do both ways:

<pre><code>NSURLComponents *components = [[NSURLComponents alloc] init];
NSArray *items = [NSArray arrayWithObjects:[NSURLQueryItem queryItemWithName:@"name" value:@"Value +"], nil];
components.queryItems = items;
NSLog(@"URL queryItems: %@", [components queryItems]);
NSLog(@"URL string before: %@", [components string]);

// Replace all "+" in the percentEncodedQuery with "%2B" (a percent-encoded +) and then replace all "%20" (a percent-encoded space) with "+"
components.percentEncodedQuery = [[components.percentEncodedQuery stringByReplacingOccurrencesOfString:@"+" withString:@"%2B"] stringByReplacingOccurrencesOfString:@"%20" withString:@"+"];
NSLog(@"URL string after: %@", [components string]);

// This is the reverse if you receive a URL with a query in that form and want to parse it with queryItems
components.percentEncodedQuery = [[components.percentEncodedQuery stringByReplacingOccurrencesOfString:@"+" withString:@"%20"] stringByReplacingOccurrencesOfString:@"%2B" withString:@"+"];
NSLog(@"URL string back: %@", [components string]);
NSLog(@"URL queryItems: %@", [components queryItems]);
</code></pre>
 
 The output is:

<pre><code>URL queryItems: (
 "&lt;NSURLQueryItem 0x100502460&gt; {name = name, value = Value +}"
)

URL string before: ?name=Value%20+

URL string after: ?name=Value+%2B

URL string back: ?name=Value%20+

URL queryItems: (
 "&lt;NSURLQueryItem 0x1002073e0&gt; {name = name, value = Value +}"
)
</code></pre>
</blockquote>

blocks|key|5605615|text|当内容类型是application/x-www-form-urlencoded时，%2B可能是一个有效字符，请参见the+link，因此NSURLComponents不会对其进行编码。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|5605616|苹果还提到了this|5605617|URLRFC3986指定必须在|5605618|的查询组件中对哪些字符进行百分比编码，但不指定应如何解释这些字符。使用带分隔符的键值对是一种常见的约定，但规范并未对其进行标准化。因此，您可能会遇到与遵循此约定的其他实现的互操作性问题。|blockquote|5605619|5605620|潜在互操作性问题的一个值得注意的示例是加号(%2B)字符的处理方式：|5605621|根据RFC3986，加号是查询中的有效字符，不需要进行百分号编码。但是，根据W3C对URI寻址的建议，加号是作为查询字符串(例如，?greeting=hello%2Bworld)中的空格的速记符号保留的。|5605622|如果URL查询组件包含根据RFC+3339格式化的日期，且时区偏移量中带有加号(例如，2013-12-31T14:00:00%2B00:00)，则将加号解释为空格会导致时间格式无效。RFC3339指定应如何格式化日期，但不建议加号是否必须在URL中进行百分号编码。根据接收此URL的实现，您可能需要对加号字符进行抢占百分号编码。|5605623|另一种方法是，考虑以更健壮的数据交换格式(如JSON或XML+)编码复杂和/或可能有问题的数据。|5605624|5605625|结论是你可能会也可能不会编码'%2B‘。|5605626|在我看来，NSURLComponents只编码它确定应该编码字符，如'&'，'=‘或像’你‘’好‘这样的汉字，它不编码字符可能根据内容类型编码或不编码，如我上面提到的'%2B’。因此，如果你发现你必须编码'%2B‘或者你的服务器不能正确解析，你可以使用下面的代码。|5605627|我不知道swift，所以我只提供了objective-c代码，很抱歉。|5605628|-+(NSString+*)URLEncodingValue:(NSString+*)value
{
++++NSCharacterSet+*set+=+[NSCharacterSet+URLQueryAllowedCharacterSet];
++++NSMutableCharacterSet+*mutableQueryAllowedCharacterSet+=+[set+mutableCopy];
++++[mutableQueryAllowedCharacterSet+removeCharactersInString:@"!*'();:@&=%2B$,/?%25#[]"];
++++return+[value+stringByAddingPercentEncodingWithAllowedCharacters:mutableQueryAllowedCharacterSet];
}|code-block|syntax|javascript|5605629|!*'();:@&=%2B$,/?%25#[]是RFC3986中定义的保留字符，代码将对它们进行编码，它们都出现在value参数中，如果您只想编码'%2B'，只需将!*'();:@&=%2B$,/?%25#[]替换为%2B即可。|5605630|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/questions/2678551/when-to-encode-space-to-plus-or-20|1|https://developer.apple.com/reference/foundation/nsurlcomponents/1407752-queryitems|2|https://en.wikipedia.org/wiki/Percent-encoding^0|15|1|1U|F|1J|8|0|0|6|4|1|0|0|0|0|0|0|0|0|0|0|5|F|0|0|0|24|J|2Q|1|0|J|2|0^^$0|@$1|2|3|4|5|6|7|1L|8|@$9|1M|A|1N|B|C]|$9|1O|A|1P|B|C]]|D|@$9|1Q|A|1R|1|1S]]|E|$]]|$1|F|3|G|5|6|7|1T|8|@]|D|@$9|1U|A|1V|1|1W]]|E|$]]|$1|H|3|I|5|6|7|1X|8|@]|D|@]|E|$]]|$1|J|3|K|5|L|7|1Y|8|@]|D|@]|E|$]]|$1|M|3|-4|5|6|7|1Z|8|@]|D|@]|E|$]]|$1|N|3|O|5|6|7|20|8|@]|D|@]|E|$]]|$1|P|3|Q|5|6|7|21|8|@]|D|@]|E|$]]|$1|R|3|S|5|6|7|22|8|@]|D|@]|E|$]]|$1|T|3|U|5|6|7|23|8|@]|D|@]|E|$]]|$1|V|3|-4|5|6|7|24|8|@]|D|@]|E|$]]|$1|W|3|X|5|6|7|25|8|@]|D|@]|E|$]]|$1|Y|3|Z|5|6|7|26|8|@$9|27|A|28|B|C]]|D|@]|E|$]]|$1|10|3|11|5|6|7|29|8|@]|D|@]|E|$]]|$1|12|3|13|5|14|7|2A|8|@]|D|@]|E|$15|16]]|$1|17|3|18|5|6|7|2B|8|@$9|2C|A|2D|B|C]|$9|2E|A|2F|B|C]]|D|@$9|2G|A|2H|1|2I]]|E|$]]|$1|19|3|-4|5|6|7|2J|8|@]|D|@]|E|$]]]|1A|$1B|$5|1C|1D|1E|E|$1F|1G]]|1H|$5|1C|1D|1E|E|$1F|1I]]|1J|$5|1C|1D|1E|E|$1F|1K]]]]

<code>+</code> may be a valid character when the content-type is application/x-www-form-urlencoded, see <a href="https://stackoverflow.com/questions/2678551/when-to-encode-space-to-plus-or-20">the link</a>, so <code>NSURLComponents</code> doesn't encode it.

Apple also mention <a href="https://developer.apple.com/reference/foundation/nsurlcomponents/1407752-queryitems" rel="nofollow noreferrer">this</a>:

<blockquote>
 RFC 3986 specifies which characters must be percent-encoded in the
 query component of a URL, but not how those characters should be
 interpreted. The use of delimited key-value pairs is a common
 convention, but isn't standardized by a specification. Therefore, you
 may encounter interoperability problems with other implementations
 that follow this convention.
 
 One notable example of potential interoperability problems is how the
 plus sign (+) character is handled:
 
 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).
 
 If a URL query component contains a date formatted according to RFC
 3339 with a plus sign in the timezone offset (for example,
 2013-12-31T14:00:00+00:00), interpreting the plus sign as a space
 results in an invalid time format. RFC 3339 specifies how dates should
 be formatted, but doesn't advise whether the plus sign must be
 percent-encoded in a URL. Depending on the implementation receiving
 this URL, you may need to preemptively percent-encode the plus sign
 character.
 
 As an alternative, consider encoding complex and/or potentially
 problematic data in a more robust data-interchange format, such as
 JSON or XML.
</blockquote>

The conclude is you may or may not encode '+'.

In my opinion, <code>NSURLComponents</code> only encode character which it make sure that should be encoded, such as '&amp;', '=' or Chinese characters like '你' '好', it doesn't encode the character may be encode or not according to the content-type, like '+' I mentioned above. So if you find you have to encode '+' or your server can't parse correctly, you can use the code below.

I don't know swift, so I just provide objective-c code, sorry for that.

<pre><code>- (NSString *)URLEncodingValue:(NSString *)value
{
 NSCharacterSet *set = [NSCharacterSet URLQueryAllowedCharacterSet];
 NSMutableCharacterSet *mutableQueryAllowedCharacterSet = [set mutableCopy];
 [mutableQueryAllowedCharacterSet removeCharactersInString:@"!*'();:@&amp;=+$,/?%#[]"];
 return [value stringByAddingPercentEncodingWithAllowedCharacters:mutableQueryAllowedCharacterSet];
}
</code></pre>

<a href="https://en.wikipedia.org/wiki/Percent-encoding" rel="nofollow noreferrer">!*'();:@&amp;=+$,/?%#[]</a> are reserved characters defined in RFC 3986, the code will encode all of them appear in the value parameter, if you just want to encode '+', just replace <code>!*'();:@&amp;=+$,/?%#[]</code> with <code>+</code>.

blocks|key|454230|text|正如其他答案所提到的，默认情况下"%2B“不是在iOS上编码的。但如果您的服务器需要对其进行编码，以下是如何进行编码的方法：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|454231|var+comps+=+URLComponents(url:+self,+resolvingAgainstBaseURL:+true)
//+a+local+var+is+needed+to+fix+a+swift+warning+about+"overlapping+accesses"+caused+by+writing+to+the+same+property+that's+being+read.
var+compsCopy+=+comps
compsCopy?.queryItems+=+[URLQueryItem(name:+"name",+value:+"abc%2Bdef")]
comps?.percentEncodedQuery+=+compsCopy?.percentEncodedQuery?.replacingOccurrences(of:+"%2B",+with:+"%252B")|code-block|syntax|javascript|454232|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

As the other answers mention, "+" isn't encoded on iOS by default. But if your server requires that to be encoded, here's how to do it:

<pre><code>var comps = URLComponents(url: self, resolvingAgainstBaseURL: true)
// a local var is needed to fix a swift warning about "overlapping accesses" caused by writing to the same property that's being read.
var compsCopy = comps
compsCopy?.queryItems = [URLQueryItem(name: "name", value: "abc+def")]
comps?.percentEncodedQuery = compsCopy?.percentEncodedQuery?.replacingOccurrences(of: "+", with: "%2B")
</code></pre>

I'm using NSURLComponents and I can't seem to get the query values to encode correctly. I need the final URL to represent a <code>+</code> as <code>%2B</code>.

<pre><code>let baseUrl = NSURL(string: "http://www.example.com") 
let components = NSURLComponents(URL: baseUrl, resolvingAgainstBaseURL: true)
components.queryItems = [ NSURLQueryItem(name: "name", value: "abc+def") ]
XCTAssertEqual(components!.string!, "http://www.example.com?connectionToken=abc%2Bdef")
</code></pre>

Failed!

Output equals:

<pre><code>http://www.example.com?connectionToken=abc+def 
</code></pre>

NOT 

<pre><code>http://www.example.com?connectionToken=abc%2Bdef
</code></pre>

I've tried several variations and I just can't seem to get it to output <code>%2B</code> at all.

How to encode + into %2B with NSURLComponents

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我使用的是NSURLComponents，但我似乎无法获得正确编码的查询值。我需要最终的网址表示为%2B的+。let baseUrl = NSURL(string: "http://www.example.com")    let components = NSURLComponents(URL: baseUrl, r...

问如何使用NSURLComponents将+编码为%2B
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问如何使用NSURLComponents将+编码为%2BEN