Objective-C - How to convert NSString to escaped J

Question

I have a NSString that may contain quotes,\, /, \r, \n, and I want to convert it to a JSON encoded string so strings like this

"text1\text2"

becomes

\"text1\\text2\"

Is there a existing function to let me do this?

Also, I am using SBJson in my project but I cannot find whether SBJson can do this or not.

NSJSONSerialization is not on the table since my application still needs to support OSX 10.6

Answer 1

Does this answer your question?

-(NSString *)JSONString:(NSString *)aString {
    NSMutableString *s = [NSMutableString stringWithString:aString];
    [s replaceOccurrencesOfString:@"\"" withString:@"\\\"" options:NSCaseInsensitiveSearch range:NSMakeRange(0, [s length])];
    [s replaceOccurrencesOfString:@"/" withString:@"\\/" options:NSCaseInsensitiveSearch range:NSMakeRange(0, [s length])];
    [s replaceOccurrencesOfString:@"\n" withString:@"\\n" options:NSCaseInsensitiveSearch range:NSMakeRange(0, [s length])];
    [s replaceOccurrencesOfString:@"\b" withString:@"\\b" options:NSCaseInsensitiveSearch range:NSMakeRange(0, [s length])];
    [s replaceOccurrencesOfString:@"\f" withString:@"\\f" options:NSCaseInsensitiveSearch range:NSMakeRange(0, [s length])];
    [s replaceOccurrencesOfString:@"\r" withString:@"\\r" options:NSCaseInsensitiveSearch range:NSMakeRange(0, [s length])];
    [s replaceOccurrencesOfString:@"\t" withString:@"\\t" options:NSCaseInsensitiveSearch range:NSMakeRange(0, [s length])];
    return [NSString stringWithString:s];
}

Source: converting NSString to JSON string

Answer 2

Swift 2:

/// Escape reserved characters to produce a valid JSON String
/// For example double quotes `"` are replaced by `\"`
/// - parameters:
///   - String: an unescaped string
/// - returns: valid escaped JSON string
func JSONString(str: String?) -> String? {
    var result : String? = nil
    if let str = str {
        result = str
            .stringByReplacingOccurrencesOfString("\"", withString: "\\\"", options: .CaseInsensitiveSearch)
            .stringByReplacingOccurrencesOfString("/", withString: "\\/", options: .CaseInsensitiveSearch)
            .stringByReplacingOccurrencesOfString("\n", withString: "\\n", options: .CaseInsensitiveSearch)
            .stringByReplacingOccurrencesOfString("\u{8}", withString: "\\b", options: .CaseInsensitiveSearch)
            .stringByReplacingOccurrencesOfString("\u{12}", withString: "\\f", options: .CaseInsensitiveSearch)
            .stringByReplacingOccurrencesOfString("\r", withString: "\\r", options: .CaseInsensitiveSearch)
            .stringByReplacingOccurrencesOfString("\t", withString: "\\t", options: .CaseInsensitiveSearch)
    }
    return result
}

Swift 3:

func JSONString(str: String) -> String {
    var result = str
    result = result.replacingOccurrences(of: "\"", with: "\\\"")
        .replacingOccurrences(of: "/", with: "\\/")
        .replacingOccurrences(of: "\n", with: "\\n")
        .replacingOccurrences(of: "\u{8}", with: "\\b")
        .replacingOccurrences(of: "\u{12}", with: "\\f")
        .replacingOccurrences(of: "\r", with: "\\r")
        .replacingOccurrences(of: "\t", with: "\\t")

    return result
}

Very useful to prevent error: Domain=NSCocoaErrorDomain Code=3840 "Invalid escape sequence around character 123."

Answer 3

let's do it in more-native-JSON-way ;)

If u like my answer, please star me at https://github.com/wanjochan

//trick: id(@[s]) => string => trim [] => target
//NSString *s
s=[[NSString alloc] initWithData:
  [NSJSONSerialization dataWithJSONObject:@[s] options:0 error:nil]
  encoding:NSUTF8StringEncoding];
s=[[s substringToIndex:([s length]-1)] substringFromIndex:1];

Answer 4

Swift 4 Solution

extension String {
    var stringEncodedJSON: String {
        var copy = self
        let encodingDict: [String: String] = ["\"": "\\\"", "/": "\\/", "\n": "\\n", "\u{8}": "\\b","\u{12}": "\\f", "\r": "\\r", "\t": "\\t"]
        encodingDict.forEach({ copy = copy.replacingOccurrences(of: $0, with: $1) })
        return copy
    }
}