Delizious Toolkit is an easy to use .NET library entirely written in C# that contains solutions to requirements I have faced in my (professional) life and provides ready-to-use components. I always strive for well-crafted and clean code with a solid API design (e.g. prefer composition over inheritance and favor factory methods over using constructors) and focus on object-functional programming paradigm.
Further things to mention:
- Implementation is mostly based on immutability and value semantics where applicable and useful
- Separation of object graph construction and application logic as discussed here (by the way a very interesting article about writing testable code!)
If you like or use my work and you are interested in this kind of software development let's get in touch. :)
Delizious Toolkit provides the following features:
- Matching of values that is adopted from Delizious Filtering library
- Decision trees
Upcoming features:
- Undo-Redo engine that is adopted from ImmutableUndoRedo library
If you want to get rid of procedural and complex if-the-else and switch statements to evaluate and match values, the Match type is what you are looking for. It lets you easily define value matches in a declarative, configurable and extensible way and comes with the following strategies:
| Match | What |
|---|---|
Always |
Matches always no matter what value is matched |
Never |
Matches never no matter what value is matched |
Null |
Matches when a value is a null reference |
NotNull |
Matches when a value is not a null reference |
Same |
Matches when a value is the same instance the match was given |
NotSame |
Matches when a value is not the same instance the match was given |
Equal |
Matches when a value equals an expected value the match was given (uses equality comparison) |
NotEqual |
Matches when a value does not equal an expected value the match was given (uses equality comparison) |
EqualTo |
Matches when a value is equal to an expected value the match was given (uses comparison) |
NotEqualTo |
Matches when a value is not equal to an expected value the match was given (uses comparison) |
GreaterThan |
Matches when a value is greater than an expected value the match was given (uses comparison) |
GreaterThanOrEqualTo |
Matches when a value is greater than or equal to an expected value the match was given (uses comparison) |
LessThan |
Matches when a value is less than an expected value the match was given (uses comparison) |
LessThanOrEqualTo |
Matches when a value is less than or equal to an expected value the match was given (uses comparison) |
All |
Matches when a value matches all of the given matches |
Any |
Matches when a value matches any of the given matches |
None |
Matches when a value matches none of the given matches |
Except |
(obsolete) Matches when a value matches none of the given matches |
Custom |
Matches when a value matches the given custom match |
Transform |
Transforms a current value into a transformed value first and then matches the transformed value with a given match |
The following sample shows the use of composition to combine different matches:
// Match when value <= -1 or value == 2 or (value => 4 and value < 7) or value > 10
var match = Match.Any(Match.LessThanOrEqualTo(-1),
Match.EqualTo(2),
Match.All(Match.GreaterThanOrEqualTo(4),
Match.LessThan(7)),
Match.GreaterThan(10));
var values = Enumerable.Range(-5, 20);
Console.WriteLine("Match when value <= -1 or value == 2 or (value => 4 and value < 7) or value > 10");
foreach (var value in values)
{
var result = match.Matches(value);
Console.WriteLine($"Match value {value}: {result}");
}
/* Output:
Match when value <= -1 or value == 2 or(value => 4 and value < 7) or value > 10
Match value -5: True
Match value -4: True
Match value -3: True
Match value -2: True
Match value -1: True
Match value 0: False
Match value 1: False
Match value 2: True
Match value 3: False
Match value 4: True
Match value 5: True
Match value 6: True
Match value 7: False
Match value 8: False
Match value 9: False
Match value 10: False
Match value 11: True
Match value 12: True
Match value 13: True
Match value 14: True
*/Making decisions that goes beyond a boolean result provided by matching of values is where decision trees come into the game. This library provides an implementation of a generic DecisionTree that supports Composite, Decision and Result nodes. You can specify both the decision trees context that is used to make decisions and the result it provides. Decisions are specified by matches using a given context.
enum CarType
{
CityCar,
Subcompact,
Compact,
MidSize,
FullSize
}
class Customer
{
public int Age { get; set; }
public int Budget { get; set; }
public override string ToString()
=> $"Age: {this.Age}, Budget: {this.Budget}";
}
static Match<Customer> MatchProperty<T>(Func<Customer, T> value, Match<T> match)
=> Match.Transform(value, match);
var decisionTree = DecisionTree.Composite(DecisionTree.Decision(MatchProperty(s => s.Budget,
Match.LessThan(8000)),
DecisionTree.Result<Customer, CarType>(CarType.CityCar)),
DecisionTree.Decision(Match.Any(MatchProperty(s => s.Age,
Match.LessThanOrEqualTo(21)),
MatchProperty(s => s.Budget,
Match.LessThan(10000))),
DecisionTree.Result<Customer, CarType>(CarType.Subcompact)),
DecisionTree.Decision(Match.Always<Customer>(),
DecisionTree.Result<Customer, CarType>(CarType.Compact)),
DecisionTree.Decision(Match.Any(
MatchProperty(s => s.Age,
Match.GreaterThanOrEqualTo(25)),
MatchProperty(s => s.Budget,
Match.GreaterThanOrEqualTo(25000))),
DecisionTree.Result<Customer, CarType>(CarType.MidSize)),
DecisionTree.Decision(MatchProperty(s => s.Budget,
Match.GreaterThanOrEqualTo(50000)),
DecisionTree.Result<Customer, CarType>(CarType.FullSize))
);
var customers = new[]
{
new Customer { Age = 18, Budget = 7999 },
new Customer { Age = 18, Budget = 12000 },
new Customer { Age = 21, Budget = 25000 },
new Customer { Age = 22, Budget = 9999 },
new Customer { Age = 22, Budget = 10000 },
new Customer { Age = 24, Budget = 24999 },
new Customer { Age = 24, Budget = 25000 },
new Customer { Age = 25, Budget = 24999 },
new Customer { Age = 50, Budget = 9999 },
new Customer { Age = 50, Budget = 50000 },
};
foreach (var customer in customers)
{
var recommendedCarTypes = decisionTree.All(customer);
var recommendations = string.Join(", ", recommendedCarTypes);
Console.WriteLine($"{customer} = {recommendations}");
}
/* Output:
Age: 18, Budget: 12000 = Subcompact, Compact
Age: 21, Budget: 25000 = Subcompact, Compact, MidSize
Age: 22, Budget: 9999 = Subcompact, Compact
Age: 22, Budget: 10000 = Compact
Age: 24, Budget: 24999 = Compact
Age: 24, Budget: 25000 = Compact, MidSize
Age: 25, Budget: 24999 = Compact, MidSize
Age: 50, Budget: 9999 = Subcompact, Compact, MidSize
Age: 50, Budget: 50000 = Compact, MidSize, FullSize
*/MIT License
Copyright (c) 2020-2021 Oliver Zick
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