Defensive coding: Possible of T

Possible<T>

Provides a type Possible<T> that abstracts away null.

Examples

Introduction

• One can convert any object to IPossible

var possible = Possible.From(1);
possible = 1.ToPossible();

• That way, when an object contains null, and you wouldn't know it beforehand the Possible class will take that into account for you:

int? nullableInt = null;
var possibleIntFromNullableViaStaticMethod = Possible.From(nullableInt);
var posibleIntFromNullableViaExtensionMethod = nullableInt.ToPossible();

object @object = null;
var possibleObjectViaStaticMethod = Possible.From(@object);
var possibleObjectViaExtensionMethod = @object.ToPossible();

• You can pass in an optional lambda to determine whether an object is null or not, used below is the default expression when you pass no lambda which just checks whether the object is not null, then Possible.From assumes you have a value by "convention":

object @object = null;
var possibleObjectViaStaticMethod = Possible.From(@object, o => o != null);
possibleObjectViaExtensionMethod = @object.ToPossible(o => o != null);

• For string objects you can define a parsing strategy, the default one is StringValueParserStrategy.NullEmptyOrWhitespaceIsNoValue which translates to String.IsNullOrWhiteSpace()

var possibleStringViaStaticMethod = Possible.From(" ");
var possibleStringViaExtensionMethod = " ".ToPossible();
possibleStringViaStaticMethod = Possible.From(" ", StringValueParserStrategy.NullOrEmptyIsNoValue);
possibleStringViaExtensionMethod = " ".ToPossible(StringValueParserStrategy.NullOrEmptyIsNoValue);

• Given a possible object, one can get the original value back, but since you have no idea whether it contains a value or not, you are always obliged to pass in either a fixed default value or a function the produces a default value

var possible = "".ToPossible();
var real = possible.GetValue(""); // pass in a fixed value as the default
real = possible.GetValue(() => String.Empty); // pass in a function the produces a default value

More in depth examples

• Concrete examples in example project: https://github.com/KodeFoxx/Common/blob/master/Examples/Kf.Common/Defensive/Possibly/Kf.Common.Defensive.Possibly.Examples/Program.cs
• Testcases: https://github.com/KodeFoxx/Common/tree/master/Source/Kf.Common.Tests/Defensive/Possibly