Could I pass some model into the template?

[ignatandrei]

I cannot see in the examples if I can pass some Model to the template. It is possible ?

[ignatandrei]

Or how I could interfere with outside code ?

[atifaziz]

At present, I have designed two modes of operation depending on the first parsed token of the template:

1. If the first token is a text literal then a simple partial class is written based on the file name plus the Template suffix. The class will have a single, private, instance-based and parameter-less method called RenderCore.
2. If the first token is code ({%…%}) then you are responsible for providing the entire class and method definition, thus having complete control over what and how you allow to be passed as a model (e.g. via one or more parameters).

In either mode, you have to provide two additional methods that must have the following signatures:

• WriteText(string value): called to emit literal text tokens of the template
• WriteValue(object value): called to emit the text for a run-time value

In fact, the second method can have overloads to avoid boxing. There is no requirement that the value parameter be typed as object.

An example of 1 is the HelloWorld.cstt sample:

Transplator/eg/HelloWorld.cstt

Lines 1 to 6 in ee1cb57

	Hello world!
	{%~ var now = DateTime.Now -%}
	Today, the date is {% now.ToString("MMM dd, yyyy") %}.
	The current time is {% now.ToString("HH:mm") %}.

This will generate a partial class called HelloWorldTemplate with a RenderCore method.

In the sample project, the partial definition is then completed in Program.cs:

Transplator/eg/Program.cs

Lines 30 to 40 in ee1cb57

	partial class HelloWorldTemplate : Template
	{
	HelloWorldTemplate(StringBuilder? sb = null) : base(sb) {}
	public static string Render()
	{
	var template = new HelloWorldTemplate();
	template.RenderCore();
	return template.ToString();
	}
	}

It inherits from Template that provides implementations for WriteText and WriteValue that emit to a StringBuilder:

Transplator/eg/Program.cs

Lines 17 to 28 in ee1cb57

	abstract class Template
	{
	readonly StringBuilder _sb;
	protected Template(StringBuilder? sb = null) =>
	_sb = sb ?? new StringBuilder();
	protected void WriteText(string value) => _sb.Append(value);
	protected void WriteValue(object value) => _sb.Append(value);
	public override string ToString() => _sb.ToString();
	}

There is no requirement for inheritance. This is just one setup I came up with for the samples.

The usage is then a simple call to the public and static Render method:

Transplator/eg/Program.cs

Line 4 in ee1cb57

Console.Write(HelloWorldTemplate.Render());

An example of mode 2 is Parameters.cstt:

Transplator/eg/Parameters.cstt

Lines 1 to 24 in ee1cb57

	{%
	using System.Collections.Generic;
	using System.Linq;
	using System.Text;
	static partial class ParametersTemplate
	{
	public static string Render(IEnumerable<string> ordinals)
	{
	var sb = new StringBuilder();
	-%}
	<ul>
	{%~ foreach (var e in ordinals.Select((ord, i) => new { Num = i + 1, Ord = ord })) { ~%}
	<li>{% e.Num %}. {% e.Ord %}</li>
	{%~ } ~%}
	</ul>
	{%
	return sb.ToString();
	void WriteText(string value) => sb.Append(value);
	void WriteValue(object value) => sb.Append(value);
	}
	}
	~%}

As you can see, you have to provide the complete surrounding class and rendering method. You can name and define the class and method as you like. What's more, the rendering method can have whatever parameters you need. The model in the case above is a sequence of strings (ordinals). Also, ParametersTemplate does not inherit from Template as in the case of HelloWorldTemplate and provides the WriteText and WriteValue methods as local functions. It goes to show that you have complete freedom.

In the first mode of operation, you can also provide a model, but it would have to be done out-of-band with the RenderCore method that is generated. Suppose we change HelloWorld.cstt so that it refers to some Time model instead of using the DateTime.Now static:

Hello world!

Today, the date is {% Time.ToString("MMM dd, yyyy") %}.
The current time is {% Time.ToString("HH:mm") %}.

Here is how then you would adapt HelloWorldTemplate to allow passing the model:

partial class HelloWorldTemplate : Template
{
    HelloWorldTemplate(DateTime time, StringBuilder? sb = null) : base(sb) => Time = time;

    DateTime Time { get; }

    public static string Render(DateTime time)
    {
        var template = new ModelTemplate(time);
        template.RenderCore();
        return template.ToString();
    }
}

The public and static Render method now takes the model and make it available with the Time property (initialized through a private constructor).

Hope this sheds some light into options for passing the model.

[ignatandrei]

Thanks!