CODEWITHSUNDEEP
c#replace
Michael Bethke
Michael Bethke

Reputation: 180

Replace many variable-length placeholders in string

Good evening,

I'm trying to find all occurrences of a string which starts with "{", and ends with "}", then replace them with a different string. To help illustrate, following is a short example.

string exampleString = "My name is {Name}. I was born as {Race}. I am {Height} tall. My hair is {HairLength}.";

In the above string, I want to remove {Name}, {Race}, {Height}, and {HairLength}, and replace them with something else. I'm having trouble with substrings right now, I think, in that I can't seem to split the string in the right place, so as only to remove the words in brackets.

I think I've kinda burnt myself out with this, and have made some silly errors, but I can't see them right now. The (messy) code I'm using to split the string is below.

public static string ForPlayer ( string originalString )
{

    string richText = originalString;

    PropertyInfo propertyInfo;
    int openingInstance = 0;
    int closingInstance = 0;

    int length = 0;
    foreach ( char c in originalString.ToCharArray ())
    {

        if ( c == '{' )
        {

            openingInstance = length;
        }

        if (  c == '}' && openingInstance > closingInstance )
        {

            int lastBrace = closingInstance;
            closingInstance = length;
            int lengthToNextBrace = originalString.IndexOf ( "{", closingInstance ) - closingInstance - 1;

            string richInstance = originalString.Substring ( openingInstance + 1, closingInstance - openingInstance - 1 );
            propertyInfo = Player.player.GetType ().GetProperty ( richInstance );
            if ( propertyInfo != null )
            {

                string beginning;
                string end;

                if ( lastBrace == 0 )
                {

                    beginning = originalString.Substring ( 0, openingInstance );
                } else
                {

                    beginning = originalString.Substring ( closingInstance + 1, openingInstance - lastBrace );
                }

                if ( lengthToNextBrace > -1 )
                {

                    end = originalString.Substring ( closingInstance + 1, lengthToNextBrace );
                } else
                {

                    end = originalString.Substring ( closingInstance + 1, originalString.Length - closingInstance - 1 );
                }

                richText = beginning + propertyInfo.GetValue ( Player.player, null ) + end;
                UnityEngine.Debug.Log ( beginning + propertyInfo.GetValue ( Player.player, null ) + end );
            }
        }

        length += 1;
    }

    return richText;
}

I'm getting:

DEBUG: "My name is default. I was born as "

DEBUG: ". I am {Height} tdefault. I am "

DEBUG: " tall. Mdefault tall. My hair is "

ERROR: "ArgumentOutOfRangeException: startIndex + length > this.length"

I would like:

My name is defaultName. I was born as 

defaultRace. I am 

defaultHeight tall. My hair is 

defaultHairLength.

===Edit===

Thank you for the answers, everyone! Unfortunately, I don't know what the string that I want to replace will be, and there are so many possibilities, that I'd rather use my current method of finding it via reflection, if possible.

Upvotes: 0

Views: 1391

Answers (5)

Gabe
Gabe

Reputation: 86778

Here's a clean, simple version. It uses the IndexOf method find braces rather than iterating over characters. It also uses a StringBuilder to avoid copying strings where possible.

public static string ForPlayer(string originalString, object player)
{
    var type = player.GetType();
    var sb = new StringBuilder(originalString.Length);
    var lastEnd = 0;    // after the last close brace
    var start = originalString.IndexOf('{');    // start brace

    while (start != -1) // go until we run out of open braces
    {
        var end = originalString.IndexOf('}', start + 1);   // end brace
        if (end == -1)  // if there's a start brace but no end, just quit
            break;
        // copy from the end of the last string to the start of the new one
        sb.Append(originalString, lastEnd, start - lastEnd);
        // get the name of the property to look up
        var propName = originalString.Substring(start + 1, end - start - 1);
        // add in the property value
        sb.Append(type.GetProperty(propName).GetValue(player, null));
        lastEnd = end + 1;  // move the pointer to the end of the last string
        start = originalString.IndexOf('{', lastEnd);   // find the next start
    }

    // copy the end of the string
    sb.Append(originalString, lastEnd, originalString.Length - lastEnd);
    return sb.ToString();
}

Upvotes: 2

Enigmativity
Enigmativity

Reputation: 117154

Try this:

public static string ForPlayer(string originalString)
{
    return
        Regex
            .Matches(originalString, "{(.*?)}")
            .Cast<Match>()
            .Select(x => x.Groups[1].Value)
            .Select(x => new
            {
                From = x,
                To = Player.player
                    .GetType()
                    .GetProperty(x)
                    .GetValue(Player.player)
                    .ToString()
            })
            .Aggregate(originalString, (a, x) => a.Replace("{" + x.From + "}", x.To));
}

I tested this on your sample input, "My name is {Name}. I was born as {Race}. I am {Height} tall. My hair is {HairLength}.", using the following test class:

public class Player
{
    public string Name {get; set; }
    public string Race {get; set; }
    public string Height {get; set; }
    public int HairLength {get; set; }
}

var player = new Player()
{
    Name = "Fred", Race = "English", Height = "Tall", HairLength = 33
};

And got this result:

"My name is Fred. I was born as English. I am Tall tall. My hair is 33."

This is even better:

public static string ForPlayer(string originalString)
{
    return
        Regex
            .Replace(originalString, "{(.*?)}", m =>
                Player.player
                    .GetType()
                    .GetProperty(m.Groups[1].Value)
                    .GetValue(Player.player)
                    .ToString());
}

Upvotes: 2

Fung
Fung

Reputation: 3558

If the placeholders are in fact property names of your objects, then you could utilize FormatWith to do the job.

string exampleString = "My name is {Name}. I was born as {Race}. I am {Height} tall. My hair is {HairLength}.";
string replacedString = exampleString.FormatWith(Player.player);

Upvotes: 2

Libor Vytlačil
Libor Vytlačil

Reputation: 11

Here is my approach that uses Regular Expressions.

using System.Text.RegularExpressions;
...
class Program
{
    static int occurence = 0;
    static string[] defValues = new string[] { "DefName", "DefRace", "DefHeight", "DefHair" };
    static string ReplaceWithDefault(Match m)
    {
        if (occurence < defValues.Length)
            return defValues[occurence++];
        else
            return "NO_DEFAULT_VALUE_FOUND";
    }

    static void Main(string[] args)
    {
        string exampleString = "My name is {Name}. I was born as {Race}. I am {Height} tall. My hair is {HairLength}.";
        string replaced = Regex.Replace(exampleString, "\\{[^\\}]+\\}", new MatchEvaluator(ReplaceWithDefault));
        occurence = 0;
        Console.WriteLine(exampleString);
        Console.WriteLine(replaced);
    }
}

Upvotes: -1

pm100
pm100

Reputation: 50210

var replacement=new Dictionary<string,string>{
    {"Name","defaultName"},
    {"Race","defaultRace"},
    {"Height","defaultHeight"},
    {"HairLength","defaultHairLength"}
};
string exampleString="My name is {Name}. I was born as {Race}. I am {Height} tall. My hair is {HairLength}.";

foreach(var kv in replacement)
{
  exampleString = exampleString.Replace("{" + kv.Key + "}", kv.Value);
}

stealing the first part from PetSerAl

Upvotes: 0

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