swift 格式化输出 json String

用系统自带的 JSONSerialization 的 .prettyPrinted 格式化打印字典

extension Dictionary where Key: ExpressibleByStringLiteral, Value: Any {
  var showJsonString: String {
        do {
            var dic: [String: Any] = [String: Any]()
            for (key, value) in self {
                dic["\(key)"] = value
            }
            let jsonData = try JSONSerialization.data(withJSONObject: dic, options: JSONSerialization.WritingOptions.prettyPrinted)

            if let data = NSString(data: jsonData, encoding: String.Encoding.utf8.rawValue) as String? {
                return data
            } else {
                return "{}"
            }
        } catch {
            return "{}"
        }
    }
}

自己格式化打印字典

extension String {
    
    func jsonFormatPrint() -> String {
     
        if (self.starts(with: "{") || self.starts(with: "[")){
            var level = 0
            var jsonFormatString = String()
            
            func getLevelStr(level:Int) -> String {
                var string = ""
                for _ in 0..<level {
                    string.append("\t")
                }
                return string
            }
            
            for char in self {
                
                if level > 0 && "\n" == jsonFormatString.last {
                    jsonFormatString.append(getLevelStr(level: level))
                }
                
                switch char {
                    
                case "{":
                    fallthrough
                case "[":
                    level += 1
                    jsonFormatString.append(char)
                    jsonFormatString.append("\n")
                case ",":
                    jsonFormatString.append(char)
                    jsonFormatString.append("\n")
                case "}":
                    fallthrough
                case "]":
                    level -= 1;
                    jsonFormatString.append("\n")
                    jsonFormatString.append(getLevelStr(level: level));
                    jsonFormatString.append(char);
                    break;
                default:
                    jsonFormatString.append(char)
                }
            }
            return jsonFormatString;
        }
        
        return self
    }
}