Baumeister.Abstractions 0.0.1-Alpha.115

Baumeister

Baumeister (german for "master builder") is a simple tool that helps by generating builder-pattern classes for your objects.

Installation

For easy installation just use the dotnet cli

dotnet add package Baumeister.Generators

Usage

To generate a builder class for a class House you first have to add a partial class HouseBuilder. In order to make it findable for Baumeister, you have to make it a generic specialization of BuilderBase<T>.

public partial class HouseBuilder : BuilderBase<House>
{
}

After compilation you are ready to use the newly generated builder.

Examples

Simple Example

public class House
{
	public int Floors { get; }

	public int Rooms { get; }

	public bool HasGarden { get; }

	public House(string name, int floors, int rooms, bool hasGarden)
	{
		Name = name;
		Floors = floors;
		Rooms = rooms;
		HasGarden = hasGarden;
	}
}

public partial class HouseBuilder : BuilderBase<House>
{
}

class Program
{
	static void Main(string[] args)
	{
		var house = new HouseBuilder()
			.WithFloors(2)
			.WithRooms(5)
			.WithHasGarden(true)
			.Build();
	}
}

Setting Default Values in Builders

You can set type-safe default values for your generated builders without modifying your target classes.

Simply implement the partial method OnInitializeDefaults in your partial builder:

public partial class HouseBuilder : BuilderBase<House>
{
    partial void OnInitializeDefaults()
    {
        WithFloors(1);
        WithHasGarden(false);
    }
}

These defaults are used unless you override them with a WithXyz call before calling Build().

How it works

Baumeister uses the Roslyn compiler to analyze the source code of the project. It searches for classes that are specializations of BuilderBase and generates a partial class with methods that enables the builder pattern. The Build() method instantiates the object with the specified properties and returns it. For the instantiation, the builder uses the constructor with the most matching parameters. It matches the given parameters with the constructor parameters and tries to find the best match. In order to do that it uses the type and names of the properties. In case not all properties that are set are used by the constructor, the builder will use public properties to set the values.