ios - 为什么 NSLog 显式地打印出换行符？

Question

我有一个对象 (TCLesson)，维护其他对象 (TCQuestion) 的集合。

外部的描述实现如下:

-(NSString*)description
{
    return [NSString stringWithFormat:
            @"TCLesson \n"
            "welcomeMessages: \n%@ \n"
            "questionPhrases: \n%@ \n"
            "goodAnswerAcknowledgements: \n%@ \n"
            "wrongAnswerAcknowledgements: \n%@ \n"
            "questions: \n%@ \n",
            self.welcomeMessages,
            self.questionPhrases,
            self.goodAnswerAcknowledgements,
            self.wrongAnswerAcknowledgements,
            self.questions];
}

内部对象几乎相同，例如:

-(NSString*)description
{
    return [NSString stringWithFormat:
            @"TCQuestions \n"
            "question: \n%@ \n"
            "pictureFileName: \n%@ \n"
            "answers: \n%@ \n"
            "hints: \n%@ \n",
            self.question,
            self.pictureFileName,
            self.answers,
            self.hints];
}

但是当涉及到日志记录时，内部对象的描述变得疯狂，并打印出一些奇怪的格式字符，例如:

TCLesson 
welcomeMessages: 
(
    "Hi <USERNAME>, let's learn the colors!",
    "Hi <USERNAME>, let's get into this lesson about the colors!",
    "Yay! We gonna learning about the colors, <USERNAME>!"
) 
questionPhrases: 
(
    "What color is this?",
    "What is the name of this color?",
    "What color do you see on the picture?"
) 
goodAnswerAcknowledgements: 
(
    "Yay! Exactly, <USERNAME>. This color is <ANSWER>.",
    "As you said, this color is <ANSWER>.",
    "Woot! Yes, you can see <ANSWER> on the picture."
) 
wrongAnswerAcknowledgements: 
(
    "No, but I can help you.",
    "Wrong answer, but I'm here to help.",
    "Apperantly not, here is a little help."
) 
questions: 
(
    "TCQuestions \nquestion: \n<DEFAULT> \npictureFileName: \norange.jpg \nanswers: \n(\n    ORANGE,\n    GOLD\n) \nhints: \n(\n    \"It is the color of the pumpkin.\",\n    \"It is the color of the orange.\",\n    \"It is the color of the carrot.\"\n) \n",
    "TCQuestions \nquestion: \n<DEFAULT> \npictureFileName: \nyellow.jpg \nanswers: \n(\n    YELLOW,\n    AMBER,\n    LEMON\n) \nhints: \n(\n    \"It is the color of the sun.\",\n    \"It is the color of the banana.\",\n    \"It is the color of the corn.\"\n) \n"
) 

如果我能在那里阅读正确的语法，我将非常高兴。

现在怎么办？

Answer 1

由于您在 TCLesson 对象中有 TCQuestion 对象数组，当内部调用 TCLesson 的描述方法时，NSArray 的描述方法将被调用以获取问题属性，该属性再次在内部调用 TCQuestion 的描述方法。在此期间，NSArray的描述方法是对TCQuestion的格式化(将“\n”替换为“\n”)描述。

因此在返回字符串之前需要将TCLesson的描述方法中出现的“\\n”替换为“\n”。

-(NSString*)description
{
    return [[NSString stringWithFormat:
            @"TCLesson \n"
            "welcomeMessages: \n%@ \n"
            "questionPhrases: \n%@ \n"
            "goodAnswerAcknowledgements: \n%@ \n"
            "wrongAnswerAcknowledgements: \n%@ \n"
            "questions: \n%@ \n",
            self.welcomeMessages,
            self.questionPhrases,
            self.goodAnswerAcknowledgements,
            self.wrongAnswerAcknowledgements,
            self.questions] stringByReplacingOccurrencesOfString:@"\\n" withString:@"\n"];
}