PlaceholderParser class final

A utility class for parsing and resolving placeholders within a string.

Supports placeholder expressions of the form:

Hello, #{user.name:Guest}! —> // Output: Hello, Alice! if user.name resolves to "Alice"
    or "Hello, Guest!" if it does not.

Supports nested placeholders and fallback values:

#{app.title:#{default.title:MyApp}}

Example usage:

final parser = PlaceholderParser(r'#{', '}', ':', r'\', false);
final result = parser.replacePlaceholders('Welcome #{user.name:Guest}', MyResolver());
print(result); // Welcome Alice or Welcome Guest

You can control:

• Prefix/suffix (e.g., #{...} or [[...]])
• Escape characters (e.g., \#{...} to skip parsing)
• Fallback separator (e.g., : or |)
• Whether to ignore unresolvable placeholders