将UTF-8编码的NSData转换为NSString

Question

我NSData从Windows服务器编码UTF-8 ,我想将其转换NSString为iPhone.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？

Answer 1

如果数据不是以null结尾,则应使用 -initWithData:encoding:

NSString* newStr = [[NSString alloc] initWithData:theData encoding:NSUTF8StringEncoding];

如果数据以空值终止,则应该使用-stringWithUTF8String:以避免最后的额外数据\0.

NSString* newStr = [NSString stringWithUTF8String:[theData bytes]];

(请注意,如果输入的UTF-8编码不正确,您将获得nil.)

Swift变种:

let newStr = String(data: data, encoding: .utf8)
// note that `newStr` is a `String?`, not a `String`.

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:))

Answer 2

你可以调用这个方法

+(id)stringWithUTF8String:(const char *)bytes.

Answer 3

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

和

@implementation NSData (EasyUTF8)

- (NSString *)asUTF8String {
    return [[NSString alloc] initWithData:self encoding:NSUTF8StringEncoding];    
}

@end

(请注意,如果您不使用ARC,则需要使用ARC autorelease.)

而不是令人震惊的冗长:

NSData *data = ...
[[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];

你可以做:

NSData *data = ...
[data asUTF8String];

Answer 4

Swift版本从String到Data再返回String:

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)
    }
}

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"

Answer 5

有时,其他答案中的方法不起作用.在我的情况下,我使用我的RSA私钥生成签名,结果是NSData.我发现这似乎有效:

Objective-C的

NSData *signature;
NSString *signatureString = [signature base64EncodedStringWithOptions:0];

迅速

let signatureString = signature.base64EncodedStringWithOptions(nil)