Overview
In many situations, you may need to transform a value before rendering it in a template. For example, you might want to format dates, numbers, or text according to specific rules. Didot provides a feature called formatters, which allows you to apply transformations to values using predefined formatting functions.
This feature enables the template engine to modify the output of a property dynamically—for instance, converting a date into a specific format or rounding a number to a given precision.
Registering a Formatter
To register a custom formatter, use the AddFormatter method of an ITemplateEngine. This method requires:
- A formatter name – an identifier for the function.
- A function delegate – defining how the value should be transformed.
Once registered, formatters can be applied to any property within the template.
Using Formatters in Templates
Once registered, a formatter can be applied to values in templates by referencing the formatter name.
var factory = new FileBasedTemplateEngineFactory();
var engine = factory.GetByTag(tag);
engine.AddFormatter("currency", (object value) => $"{value}€");
Assume the model contains a property Price, and a formatter named currency has been registered to format numbers as currency. The following examples demonstrate how to apply formatters across different template engines:
Fluid and Scriban
The price is {{ model.Price | currency }}
Handlebars
Morestachio
StringTemplate
The price is <model.Price; format=\"currency\">
Liquid and SmartFormat
This feature is not supported.
Conclusion
The formatters feature in Didot allows you to apply transformations dynamically to values before rendering, making it particularly useful for date formatting, number formatting, text transformations, and other custom processing needs. By leveraging this feature, templates remain clean, flexible, and reusable.
