c# - 递归引起的StackOverflowException

我目前正在编写一个程序来帮助编写Lore。每个Book对象可以是父对象，也可以有 child 。这意味着每个 child 都可以将 child 等无限化。我正在研究一个ToString()方法，该方法可以使用递归解决此问题，但是我一直收到StackOverflowException。

我知道这意味着什么，但是我对如何解决它有疑问。我是C#的新手，但是有很多Java经验，所以如果您知道技巧或我错过的东西，请告诉我!

所以我的问题是:如何避免StackOverflow异常？问题出在GetAllChildren()

编辑:

运行测试后，我应该得到如下信息:

Name: a
Children:
b
c
    d
e

来自@lc的代码。我得到以下输出:

Name: a
Children: No Children   b
c
e
    b
c
e
    b
c
e

这是类(class):

class Book
{
    private String name;
    private Book[] children;
    private StringBuilder text;
    private Boolean isParent;

    public Book(String name, Book[] children, StringBuilder text, Boolean isParent)
    {
        this.name = name;
        this.children = children;
        this.text = text;
        this.isParent = isParent;
    }

    /**
     * Most likely all possible Constructors
     * */
    public Book(String name, Book[] children) : this(name, children, new StringBuilder("No Text"), true) { }
    public Book(String name, String text) : this(name, new Book[0], new StringBuilder(text), false) { }
    public Book(String name, StringBuilder text) : this(name, new Book[0], text, false) { }
    public Book(String name) : this(name, new Book[0], new StringBuilder("No Text"), false) { }
    public Book(Book[] children, String text) : this("Unnamed Book", children, new StringBuilder(text), true) { }
    public Book(Book[] children, StringBuilder text) : this("Unnamed Book", children, text, true) { }
    public Book(Book[] children) : this("Unnamed Book", children, new StringBuilder("No Text"), true) { }
    public Book(StringBuilder text) : this("Unnamed Book", new Book[0], text, false) { }
    public Book() : this("Unnamed Book", new Book[0], new StringBuilder("No Text"), false) { }

    public String Name
    {
        get { return name; }
        set { name = value; }
    }

    public Book[] Children
    {
        get { return children; }
        set { children = value; }
    }

    /**
     * Will Return the StringBuilder Object of this Text
     * */

    public StringBuilder Text
    {
        get { return text; }
        set { text = value; }
    }

    public Boolean IsParent
    {
        get { return isParent; }
        set { isParent = value; }
    }

    private void GetAllChildren(Book book, StringBuilder sb)
    {
        if (book.isParent)
        {
            GetAllChildren(book, sb);
        }
        else
        {
            sb.Append("\t");
            foreach (Book b in children)
            {
                sb.Append(b.Name + "\n");
            }
        }
    }

    public override String ToString()
    {
        StringBuilder sChildren = new StringBuilder("No Children");
        if (children.Length != 0)
        {
            GetAllChildren(this, sChildren);
        }

        return "Name: " + name + "\n" +
            "Children: " + sChildren.ToString();
    }
}

最佳答案

我想你的意思是:

if (book.isParent)
{
    foreach (var child in book.Children)
        GetAllChildren(child, sb);
}

否则，您将一次又一次地使用相同的参数(GetAllChildren)调用book, sb方法。

旁注-您仍然有一些问题，因为GetAllChildren中的停止条件正在遍历子级，而在不该终止的情况下(如果不是父级，则不应有子级)。它应该返回自己的名称。此外，每个 child 还应该在上面的foreach循环中附加其名称(或者实际上，每本书应该附加其自己的名称)。

旁注2-编写的方法(带有这些更改)应该确实是静态的，因为它与任何给定的实例都不相关(这使我想到下面的建议)。

建议-我建议改为以下内容(未经测试，并且需要进行一些格式方面的工作):

//name changed to reflect what it really does
//also changed to be an instance method (we no longer pass in a Book)
//added listThisBooksName parameter to allow supressing the topmost book's output
private void AppendAllChildren(StringBuilder sb, int level = 0,
    bool listThisBooksName = false)
{
    if (listThisBooksName)
    {
        //append ourself here

        //first indent however far we need to
        sb.Append(new String('\t', level));

        //now add our name
        sb.Append(this.Name);

        //and a newline (you can strip the last one later if you want)
        sb.Append('\n');
    }

    //forget the "isParent" property, just check if it has any children
    //we don't need Children.Any() because the foreach will just iterate 0 times
    //you might also consider using a List<Book> instead of an array for Children
    if (this.Children != null)
        foreach (var child in this.Children)
            child.AppendAllChildren(sb, level+1, true);
}