老外编的程序（九）：Using Indexer Properties
点击次数：22 次 发布日期：2008-11-27 01:17:00 作者：源代码网
|
using System; public class Document { // Type allowing the document to be viewed like an array of words: public class WordCollection { readonly Document document; // The containing document internal WordCollection(Document d) { document = d; } // Helper function -- search character array "text", starting at // character "begin", for word number "wordCount." Returns false // if there are less than wordCount words. Sets "start" and // length" to the position and length of the word within text: private bool GetWord(char[] text, int begin, int wordCount, out int start, out int length) { int end = text.Length; int count = 0; int inWord = -1; start = length = 0; for (int i = begin; i <= end; ++i) { bool isLetter = i < end && Char.IsLetterOrDigit(text[i]); if (inWord >= 0) { if (!isLetter) { if (count++ == wordCount) { start = inWord; length = i - inWord; return true; } inWord = -1; } } else { if (isLetter) inWord = i; } } return false; } // Indexer to get and set words of the containing document: public string this[int index] { get { int start, length; if (GetWord(document.TextArray, 0, index, out start, out length)) return new string(document.TextArray, start, length); else throw new IndexOutOfRangeException(); } set { int start, length; if (GetWord(document.TextArray, 0, index, out start, out length)) { // Replace the word at start/length with the // string "value": if (length == value.Length) { Array.Copy(value.ToCharArray(), 0, document.TextArray, start, length); } else { char[] newText = new char[document.TextArray.Length + value.Length - length]; Array.Copy(document.TextArray, 0, newText, 0, start); Array.Copy(value.ToCharArray(), 0, newText, start, value.Length); Array.Copy(document.TextArray, start + length, newText, start + value.Length, document.TextArray.Length - start - length); document.TextArray = newText; } } else throw new IndexOutOfRangeException(); } } // Get the count of words in the containing document: public int Count { get { int count = 0, start = 0, length = 0; while (GetWord(document.TextArray, start + length, 0, out start, out length)) ++count; return count; } } } // Type allowing the document to be viewed like an "array" // of characters: public class CharacterCollection { readonly Document document; // The containing document internal CharacterCollection(Document d) { document = d; } // Indexer to get and set characters in the containing document: public char this[int index] { get { return document.TextArray[index]; } set { document.TextArray[index] = value; } } // Get the count of characters in the containing document: public int Count { get { return document.TextArray.Length; } } } // Because the types of the fields have indexers, // these fields appear as "indexed properties": public readonly WordCollection Words; public readonly CharacterCollection Characters; private char[] TextArray; // The text of the document. public Document(string initialText) { TextArray = initialText.ToCharArray(); Words = new WordCollection(this); Characters = new CharacterCollection(this); } public string Text { get { return new string(TextArray); } } } class Test { static void Main() { Document d = new Document( "peter piper picked a peck of pickled peppers. How many pickled peppers did peter piper pick?" ); // Change word "peter" to "penelope": for (int i = 0; i < d.Words.Count; ++i) { if (d.Words[i] == "peter") d.Words[i] = "penelope"; } // Change character "p" to "P" for (int i = 0; i < d.Characters.Count; ++i) { if (d.Characters[i] == "p") d.Characters[i] = "P"; } Console.WriteLine(d.Text); &nb  源代码网供稿. |
