TemplateVariableResolver class abstract interface

Resolves template variable names into their string representations at runtime during template rendering.

TemplateVariableResolver provides a flexible mechanism to supply values for placeholders in templates. It abstracts how variables are looked up, computed, or fetched from external sources.

Responsibilities

• Resolve a variable name to a string that can be substituted into a template.
• Support dynamic or computed variable resolution.
• Optionally allow bulk setting of variables for later resolution.

Design Notes

• Implementations may use an internal map, lazy computation, or integrate with external services.
• Should handle unknown or missing variables gracefully:
  • Return an empty string,
  • Provide a default value, or
  • Throw a descriptive exception, depending on the use case.
• Useful in combination with TemplateContext and TemplateRenderer.

Example Implementation

class MapVariableResolver implements TemplateVariableResolver {
  final Map<String, Object?> _variables;

  MapVariableResolver([Map<String, Object?>? variables])
      : _variables = variables ?? {};

  @override
  String resolve(String variable) => _variables[variable]?.toString() ?? '';

  @override
  void setVariables(Map<String, Object?> variables) {
    _variables.clear();
    _variables.addAll(variables);
  }
}