First, most of the time you think you need something like this, you don’t; it’s a sign that you’re trying to treat Python like Java, and the solution is to step back and ask why you need a factory. Often, the simplest thing to do is to just have a constructor with defaulted/optional/keyword arguments. Even … Read more
A builder helps you construct a complex object. An example is the StringBuilder class (Java, C#), which builds the final string piece by piece. A better example is the UriComponentsBuilder in Spring, which helps you build a URI. A factory method gives you a complete object in one shot (as opposed to the builder). A … Read more
With the Factory pattern, you produce instances of implementations (Apple, Banana, Cherry, etc.) of a particular interface — say, IFruit. With the Abstract Factory pattern, you provide a way for anyone to provide their own factory. This allows your warehouse to be either an IFruitFactory or an IJuiceFactory, without requiring your warehouse to know anything … Read more
I’m very hesitant to categorize “instance versus static” as a matter of taste. This sort of implies that it’s aesthetic like a favorite color or, more appropos, camelCase versus PascalCase. Instance versus static is more a question of tradeoffs. With instance members of any kind, you get all of the benefits of polymorphism, since you … Read more
Hope this helps. It describes the various types of factories. I used the Head First Design Patterns book as my reference. I used yuml.me to diagram. Static Factory Is a class with a Static Method to product various sub types of Product. Simple Factory Is a class that can produce various sub types of Product. … Read more
All three Factory types do the same thing: They are a “smart constructor”. Let’s say you want to be able to create two kinds of Fruit: Apple and Orange. Factory Factory is “fixed”, in that you have just one implementation with no subclassing. In this case, you will have a class like this: class FruitFactory … Read more
The static factory method pattern is a way to encapsulate object creation. Without a factory method, you would simply call the class’s constructor directly: Foo x = new Foo(). With this pattern, you would instead call the factory method: Foo x = Foo.create(). The constructors are marked private, so they cannot be called except from … Read more
I like thinking about design pattens in terms of my classes being ‘people,’ and the patterns are the ways that the people talk to each other. So, to me the factory pattern is like a hiring agency. You’ve got someone that will need a variable number of workers. This person may know some info they … Read more
First of all, there are cases when object construction is a task complex enough to justify its extraction to another class. I believe this point is incorrect. The complexity doesn’t really matter. The relevance is what does. If an object can be constructed in one step (not like in the builder pattern), the constructor is … Read more
With the Factory pattern, you produce instances of implementations (Apple, Banana, Cherry, etc.) of a particular interface — say, IFruit. With the Abstract Factory pattern, you provide a way for anyone to provide their own factory. This allows your warehouse to be either an IFruitFactory or an IJuiceFactory, without requiring your warehouse to know anything … Read more