如何在Swift中创建嵌入式JSON对象并返回String？

My code.swift is below :

我的code.swift如下:

public class Test {

    var testA: String = ""                
    var testB: String = ""                 

    let T_testA : String = "testA"
    let T_testB : String = "testB"

    init(testA: String, testB: String) {
        self.testA = testA
        self.testB = testB
    }

    func toString() -> String? {
        let jsonDic : [String: AnyObject] = [
            T_testA: testA,
            T_testB: testB,
        ]
        do {
            let jsonObject = try NSJSONSerialization.dataWithJSONObject( jsonDic, options: NSJSONWritingOptions.PrettyPrinted)

            return String(data: jsonObject, encoding: NSUTF8StringEncoding)
        } catch {
            return nil
        }
    }
}
p