我想获得这些特定字母的百分比编码字符串，如何在objective-c中实现这一点？
Reserved characters after percent-encoding
! * ' ( ) ; : @ & = + $ , / ? # [ ]
%21 %2A %27 %28 %29 %3B %3A %40 %26 %3D %2B %24 %2C %2F %3F %23 %5B %5D
请使用此字符串进行测试，看看它是否有效:
myURL = @"someurl/somecontent"
我希望字符串看起来像:
myEncodedURL = @"someurl%2Fsomecontent"
我已经try 了stringByAddingPercentEscapesUsingEncoding: NSASCIIStringEncoding，但它不起作用，结果仍然与原始字符串相同.请给我一些建议.
我发现stringByAddingPercentEscapesUsingEncoding:和CFURLCreateStringByAddingPercentEscapes()都不够.NSString方法漏掉了很多字符，CF函数只允许您说出要转义的(特定)字符.正确的规范是转义除小字符集以外的所有字符.
为了解决这个问题，我创建了NSString category方法来正确编码字符串.它将对除[a-zA-Z0-9.-_~]之外的所有内容进行百分比编码，并将空格编码为+(根据this specification).它还将正确处理unicode字符的编码.
- (NSString *) URLEncodedString_ch {
NSMutableString * output = [NSMutableString string];
const unsigned char * source = (const unsigned char *)[self UTF8String];
int sourceLen = strlen((const char *)source);
for (int i = 0; i < sourceLen; ++i) {
const unsigned char thisChar = source[i];
if (thisChar == ' '){
[output appendString:@"+"];
} else if (thisChar == '.' || thisChar == '-' || thisChar == '_' || thisChar == '~' ||
(thisChar >= 'a' && thisChar <= 'z') ||
(thisChar >= 'A' && thisChar <= 'Z') ||
(thisChar >= '0' && thisChar <= '9')) {
[output appendFormat:@"%c", thisChar];
} else {
[output appendFormat:@"%%%02X", thisChar];
}
}
return output;
}