Using custom types

Using custom types

All the examples in the documents are in strings, but fixtures want to process and return other data types.

GreenPepper provides a mechanism to help conversion from String to other data types and back again.

so an example that look likes

Will match a class with the following method

public class SomeFixture {
   public SomeFixture(Ammount ammount) {...}

   public setColor(RGB color) ...
   public someBool(boolean yesNo)..
   public Ratio answer()...
}

Lets look at how GreenPepper will match these.

Converters

Converters are class implementing the interface com.greenpepper.converter.TypeConverter in java or GreenPepper.Converters.ITypeConverter in C#

public interface TypeConverter
{
    boolean canConvertTo( Class type );

    Object parse( String value, Class type );

    String toString( Object value );
}

namespace GreenPepper.Converters
{
    public interface ITypeConverter
    {
        bool CanConvertTo(Type type);

        object ValueOf(string value, Type type);

        string ToString(object value);
    }
}

Adding a new type converter

The com.greenpepper.GreenPepper class provides a method to add your own type converter

public static void register( TypeConverter converter)

public static void Register( ITypeConverter converter)

The better place to register your custom type is in a custom system under developement :

public static class CustomSystemUnderDevelopment extends DefaultSystemUnderDevelopment
    {
        public CustomSystemUnderDevelopment( String... params )
        {
           GreenPepper.register(new MyCustomTypeConverter());
        }
    }

The converters are always check in an LIFO manners. If two converters can process a data type the last one that has been register will be used. That way, you can provides your own converters in place of the standard GreenPepper converters. 

Self conversion

Instead of registering a TypeConverter, you can uses self converting types.

Self converting type implies that you add a static parse method to your class.

public static T parse(String val);
// And then to revert back to a string,
public static String toString(T value)

public static T ValueOf(string text)
// And then to revert back to a string,
public static String ToString(T value)

Your class does not have to provides both of them.

Rules of conversion 

From example to fixture

1. First GreenPepper  will look for a registered TypeConverter that can handles the type.
2. Second GreenPepper will verify if the type is can self convert (ie public static T parse(String) or public static T ValueOf(string))
3. An UnsupportedOperationException will be thrown

From fixture return value to String

1. First GreenPepper  will look for a registered TypeConverter that can handles the type. 
2. Second GreenPepper will verify if the type is can self revert (ie public static String toString(T) or public static T ToString(string))
3. Use the toString() or ToString() method on the data itself.