[英]Convert UTF-8 encoded NSData to NSString
I have UTF-8 encoded NSData
from windows server and I want to convert it to NSString
for iPhone. 我从Windows服务器有UTF-8编码的NSData
,我想将它转换为iPhone的NSString
。 Since data contains characters (like a degree symbol) which have different values on both platforms, how do I convert data to string? 由于数据包含在两个平台上具有不同值的字符(如度数符号), 如何将数据转换为字符串?
If the data is not null-terminated, you should use -initWithData:encoding:
如果数据不是以null结尾,则应使用-initWithData:encoding:
NSString* newStr = [[NSString alloc] initWithData:theData encoding:NSUTF8StringEncoding];
If the data is null-terminated, you should instead use -stringWithUTF8String:
to avoid the extra \\0
at the end. 如果数据以空值终止,则应使用-stringWithUTF8String:
以避免结尾处的额外\\0
。
NSString* newStr = [NSString stringWithUTF8String:[theData bytes]];
(Note that if the input is not properly UTF-8-encoded, you will get nil
.) (注意,如果输入没有正确的UTF-8编码,你将得到nil
。)
let newStr = String(data: data, encoding: .utf8)
// note that `newStr` is a `String?`, not a `String`.
If the data is null-terminated, you could go though the safe way which is remove the that null character, or the unsafe way similar to the Objective-C version above. 如果数据以空值终止,您可以通过删除该空字符的安全方式或类似于上述Objective-C版本的不安全方式。
// safe way, provided data is \0-terminated
let newStr1 = String(data: data.subdata(in: 0 ..< data.count - 1), encoding: .utf8)
// unsafe way, provided data is \0-terminated
let newStr2 = data.withUnsafeBytes(String.init(utf8String:))
你可以调用这个方法
+(id)stringWithUTF8String:(const char *)bytes.
I humbly submit a category to make this less annoying: 我谦卑地提交一个类别,以减少烦恼:
@interface NSData (EasyUTF8)
// Safely decode the bytes into a UTF8 string
- (NSString *)asUTF8String;
@end
and 和
@implementation NSData (EasyUTF8)
- (NSString *)asUTF8String {
return [[NSString alloc] initWithData:self encoding:NSUTF8StringEncoding];
}
@end
(Note that if you're not using ARC you'll need an autorelease
there.) (请注意,如果您不使用ARC,则需要在那里进行autorelease
。)
Now instead of the appallingly verbose: 而不是令人震惊的冗长:
NSData *data = ...
[[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
You can do: 你可以做:
NSData *data = ...
[data asUTF8String];
The Swift version from String to Data and back to String: Swift版本从String到Data再返回String:
Xcode 10.1 • Swift 4.2.1 Xcode 10.1•Swift 4.2.1
extension Data {
var string: String? {
return String(data: self, encoding: .utf8)
}
}
extension StringProtocol {
var data: Data {
return Data(utf8)
}
}
extension String {
var base64Decoded: Data? {
return Data(base64Encoded: self)
}
}
Playground 操场
let string = "Hello World" // "Hello World"
let stringData = string.data // 11 bytes
let base64EncodedString = stringData.base64EncodedString() // "SGVsbG8gV29ybGQ="
let stringFromData = stringData.string // "Hello World"
let base64String = "SGVsbG8gV29ybGQ="
if let data = base64String.base64Decoded {
print(data) // 11 bytes
print(data.base64EncodedString()) // "SGVsbG8gV29ybGQ="
print(data.string ?? "nil") // "Hello World"
}
let stringWithAccent = "Olá Mundo" // "Olá Mundo"
print(stringWithAccent.count) // "9"
let stringWithAccentData = stringWithAccent.data // "10 bytes" note: an extra byte for the acute accent
let stringWithAccentFromData = stringWithAccentData.string // "Olá Mundo\n"
Sometimes, the methods in the other answers don't work. 有时,其他答案中的方法不起作用。 In my case, I'm generating a signature with my RSA private key and the result is NSData. 在我的情况下,我使用我的RSA私钥生成签名,结果是NSData。 I found that this seems to work: 我发现这似乎有效:
Objective-C Objective-C的
NSData *signature;
NSString *signatureString = [signature base64EncodedStringWithOptions:0];
Swift 迅速
let signatureString = signature.base64EncodedStringWithOptions(nil)
Just to summarize, here's a complete answer, that worked for me. 总结一下,这是一个完整的答案,对我有用。
My problem was that when I used 我的问题是我用的时候
[NSString stringWithUTF8String:(char *)data.bytes];
The string I got was unpredictable: Around 70% it did contain the expected value, but too often it resulted with Null
or even worse: garbaged at the end of the string. 我得到的字符串是不可预测的:大约70%它确实包含了预期的值,但是它常常导致Null
甚至更糟:在字符串的末尾打扮。
After some digging I switched to 经过一番挖掘后,我转而去了
[[NSString alloc] initWithBytes:(char *)data.bytes length:data.length encoding:NSUTF8StringEncoding];
And got the expected result every time. 每次都得到预期的结果。
With Swift 5, you can use String
's init(data:encoding:)
initializer in order to convert a Data
instance into a String
instance using UTF-8. 使用Swift 5,您可以使用String
的init(data:encoding:)
初始化程序,以便使用UTF-8将Data
实例转换为String
实例。 init(data:encoding:)
has the following declaration: init(data:encoding:)
具有以下声明:
init?(data: Data, encoding: String.Encoding)
Returns a
String
initialized by converting given data into Unicode characters using a given encoding. 返回通过使用给定编码将给定数据转换为Unicode字符而初始化的String
。
The following Playground code shows how to use it: 以下Playground代码显示了如何使用它:
import Foundation
let json = """
{
"firstName" : "John",
"lastName" : "Doe"
}
"""
let data = json.data(using: String.Encoding.utf8)!
let optionalString = String(data: data, encoding: String.Encoding.utf8)
print(String(describing: optionalString))
/*
prints:
Optional("{\n\"firstName\" : \"John\",\n\"lastName\" : \"Doe\"\n}")
*/
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