Replacing dynamic variable in string UNITY - regex

Question

I am making a simple dialogue system, and would like to "dynamise" some of the sentences.
For exemple, I have a Sentence
Hey Adventurer {{PlayerName}} !
Welcome in the world !
Now In code I am trying to replace that by the real value of the string in my game. I am doing something like this. But it doesn't work. I do have a string PlayerName in my component where the function is situated
Regex regex = new Regex("(?<={{)(.*?)(?=}})");
MatchCollection matches = regex.Matches(sentence);
for(int i = 0; i < matches.Count; i++)
{
Debug.Log(matches[i]);
sentence.Replace("{{"+matches[i]+"}}", this.GetType().GetField(matches[i].ToString()).GetValue(this) as string);
}
return sentence;
But this return me an error, even tho the match is correct.
Any idea of a way to do fix, or do it better?

Answer 1

Here's how I would solve this.
Create a dictionary with keys as the values you wish to replace and values as what you will be replacing them to.
Dictionary<string, string> valuesToReplace;
valuesToReplace = new Dictionary<string, string>();
valuesToReplace.Add("[playerName]", "Max");
valuesToReplace.Add("[day]", "Thursday");
Then check the text for the values in your dictionary.
If you make sure all of your keys start with "[" and end with "]" this will be quick and easy.
List<string> replacements = new List<string>();
//We will save all of the replacements we are about to perform here.
//This is done so we won't be modifying the original string while working on it, which will create problems.
//We will save them in the following format: originalText}newText
for(int i = 0; i < text.Length; i++) //Let's loop through the entire text
{
int startOfVar = 9999;
if(text[i] == '[') //We have found the beginning of a variable
{
startOfVar = i;
}
if(text[i] == ']') //We have found the ending of a variable
{
string replacement = text.Substring(startOfVar, i - startOfVar); //We have found the section we wish to replace
if (valuesToReplace.ContainsKey(replacement))
replacements.Add(replacement + "}" + valuesToReplace[replacement]); //Add the replacement we are about to perform to our dictionary
}
}
//Now let's perform the replacements:
foreach(string replacement in replacements)
{
text = text.Replace(replacement.Split('}')[0], replacement.Split('}')[1]); //We split our line. Remember the old value was on the left of the } and the new value was on the right
}
This will also work much faster, since it allows you to add as many variables as you wish without making the code slower.

Answer 2

Using Regex.Replace method, and a MatchEvaluator delegate (untested):
Dictionary<string, string> Replacements = new Dictionary<string, string>();
Regex DialogVariableRegex = new Regex("(?<={{)(.*?)(?=}})");
string Replace(string sentence) {
DialogVariableRegex.Replace(sentence, EvaluateMatch);
return sentence;
}
string EvaluateMatch(Match match) {
var matchedKey = match.Value;
if (Replacements.ContainsKey(matchedKey))
return Replacements[matchedKey];
else
return ">>MISSING KEY<<";
}

Answer 3

This is kind of old now, but I figured I'd update the accepted code above. It won't work since the start index is reset every time the loop iterates, so setting startOfVar = i gets completely reset by the time it hits the closing character. Plus there are problems if there's an open bracket '[' and no closing one. You can also no longer use those brackets in your text.
There's also setting the splitter to a single character. It tests fine, but if I set my player name to "Rob}ert", that will cause problems when it performs the replacements.
Here is my updated take on the code which I've tested works in Unity:
public string EvaluateVariables(string str)
{
Dictionary<string, string> varDict = GetVariableDictionary();
List<string> varReplacements = new List<string>();
string matchGuid = Guid.NewGuid().ToString();
bool matched = false;
int start = int.MaxValue;
for (int i = 0; i < str.Length; i++)
{
if (str[i] == '{')
{
if (str[i + 1] == '$')
{
start = i;
matched = true;
}
}
else if (str[i] == '}' && matched)
{
string replacement = str.Substring(start, (i - start) + 1);
if (varDict.ContainsKey(replacement))
{
varReplacements.Add(replacement + matchGuid + varDict[replacement]);
}
start = int.MaxValue;
matched = false;
}
}
foreach (string replacement in varReplacements)
{
str = str.Replace(replacement.Split(new string[] { matchGuid }, StringSplitOptions.None)[0], replacement.Split(new string[] { matchGuid }, StringSplitOptions.None)[1]);
}
return str;
}
private Dictionary<string, string> GetVariableDictionary()
{
Dictionary<string, string> varDict = new Dictionary<string, string>();
varDict.Add("{$playerName}", playerName);
varDict.Add("{$npcName}", npcName);
return varDict;
}