我正在尝试构建一个字符串扩展方法,将字符串剪裁到一定长度,但不会破坏单词。我想检查框架中是否有任何内置或者比我更聪明的方法。到目前为止,这是我的(未经过全面测试):
public static string SmartTrim(this string s, int length)
{
StringBuilder result = new StringBuilder();
if (length >= 0)
{
if (s.IndexOf(' ') > 0)
{
string[] words = s.Split(' ');
int index = 0;
while (index < words.Length - 1 && result.Length + words[index + 1].Length <= length)
{
result.Append(words[index]);
result.Append(" ");
index++;
}
if (result.Length > 0)
{
result.Remove(result.Length - 1, 1);
}
}
else
{
result.Append(s.Substring(0, length));
}
}
else
{
throw new ArgumentOutOfRangeException("length", "Value cannot be negative.");
}
return result.ToString();
}
答案 0 :(得分:14)
我会使用string.LastIndexOf
- 至少我们只关心空格。然后就没有必要创建任何中间字符串......
尚未经过测试:
public static string SmartTrim(this string text, int length)
{
if (text == null)
{
throw new ArgumentNullException("text");
}
if (length < 0)
{
throw new ArgumentOutOfRangeException();
}
if (text.Length <= length)
{
return text;
}
int lastSpaceBeforeMax = text.LastIndexOf(' ', length);
if (lastSpaceBeforeMax == -1)
{
// Perhaps define a strategy here? Could return empty string,
// or the original
throw new ArgumentException("Unable to trim word");
}
return text.Substring(0, lastSpaceBeforeMax);
}
测试代码:
public class Test
{
static void Main()
{
Console.WriteLine("'{0}'", "foo bar baz".SmartTrim(20));
Console.WriteLine("'{0}'", "foo bar baz".SmartTrim(3));
Console.WriteLine("'{0}'", "foo bar baz".SmartTrim(4));
Console.WriteLine("'{0}'", "foo bar baz".SmartTrim(5));
Console.WriteLine("'{0}'", "foo bar baz".SmartTrim(7));
}
}
结果:
'foo bar baz'
'foo'
'foo'
'foo'
'foo bar'
答案 1 :(得分:2)
基于Regex的解决方案怎么样?你可能想要测试更多,并做一些边界检查;但这是我心中想到的:
using System;
using System.Text.RegularExpressions;
namespace Stackoverflow.Test
{
static class Test
{
private static readonly Regex regWords = new Regex("\\w+", RegexOptions.Compiled);
static void Main()
{
Console.WriteLine("The quick brown fox jumped over the lazy dog".SmartTrim(8));
Console.WriteLine("The quick brown fox jumped over the lazy dog".SmartTrim(20));
Console.WriteLine("Hello, I am attempting to build a string extension method to trim a string to a certain length but with not breaking a word. I wanted to check to see if there was anything built into the framework or a more clever method than mine".SmartTrim(100));
}
public static string SmartTrim(this string s, int length)
{
var matches = regWords.Matches(s);
foreach (Match match in matches)
{
if (match.Index + match.Length > length)
{
int ln = match.Index + match.Length > s.Length ? s.Length : match.Index + match.Length;
return s.Substring(0, ln);
}
}
return s;
}
}
}
答案 2 :(得分:2)
试一试。它是null安全的,如果长度比字符串长,则不会中断,并且涉及更少的字符串操作。
编辑:根据建议,我删除了中间字符串。我会留下答案,因为它可能在不需要例外的情况下有用。
public static string SmartTrim(this string s, int length)
{
if(s == null || length < 0 || s.Length <= length)
return s;
// Edit a' la Jon Skeet. Removes unnecessary intermediate string. Thanks!
// string temp = s.Length > length + 1 ? s.Remove(length+1) : s;
int lastSpace = s.LastIndexOf(' ', length + 1);
return lastSpace < 0 ? string.Empty : s.Remove(lastSpace);
}
答案 3 :(得分:1)
string strTemp = "How are you doing today";
int nLength = 12;
strTemp = strTemp.Substring(0, strTemp.Substring(0, nLength).LastIndexOf(' '));
我认为应该这样做。当我跑步时,它结束了“你好吗”。
所以你的功能是:
public static string SmartTrim(this string s, int length)
{
return s.Substring(0, s.Substring(0, length).LastIndexOf(' '));;
}
我肯定会添加一些异常处理,例如确保整数长度不大于字符串长度且不小于0.
答案 4 :(得分:1)
如果您只关心空格作为单词边界,则必须使用LINQ one liner:
return new String(s.TakeWhile((ch,idx) => (idx < length) || (idx >= length && !Char.IsWhiteSpace(ch))).ToArray());
答案 5 :(得分:1)
像这样使用
var substring = source.GetSubstring(50, new string[] { " ", "." })
此方法可以根据一个或多个分隔符
获取子字符串public static string GetSubstring(this string source, int length, params string[] options)
{
if (string.IsNullOrWhiteSpace(source))
{
return string.Empty;
}
if (source.Length <= length)
{
return source;
}
var indices =
options.Select(
separator => source.IndexOf(separator, length, StringComparison.CurrentCultureIgnoreCase))
.Where(index => index >= 0)
.ToList();
if (indices.Count > 0)
{
return source.Substring(0, indices.Min());
}
return source;
}
答案 6 :(得分:0)
即使其他人已经充分回答了这个问题,我还是会考虑一些Linq的善良:
public string TrimString(string s, int maxLength)
{
var pos = s.Select((c, idx) => new { Char = c, Pos = idx })
.Where(item => char.IsWhiteSpace(item.Char) && item.Pos <= maxLength)
.Select(item => item.Pos)
.SingleOrDefault();
return pos > 0 ? s.Substring(0, pos) : s;
}
我遗漏了参数检查,其他人只是强调了重要的代码......