I thought it worth while to expound on the differences between a train wreck and method chaining.
Whereas a trainwreck is a bad idea, method chaining is an excellent idea. This blog will try to explain why these two are polar opposites on the good/bad scale, even though the syntax differs very little.
Trainwreck
A trainwreck is a bad idea. It provides an Object A with in depth knowledge of several other objects. Knowledge that should be contained in the individual objects instead of Object A.
In code it would look like follows:
public class A
{
public void someMethod(B b)
{
b.getC().getD().getE().doThing();
}
}
A Trainwreck breaks the Law of Demeter
[1] (and everyone knows, if you break a law, you have to go to jail).
A solution would be to just tell B to do it, and let it figure it out.
public class A
{
public void someMethod(B b)
{
b.doThing();
}
}
Method Chaining
Method chaining is an excellent idea. The methods used always return the Object itself. It's a good way of constructing an Object without having to resort to multiple different Constructor methods with varying (large amount of) parameters.
public class Person
{
private long id;
private String firstName;
private String lastName;
private String address;
private String telephone;
private String title;
public Person(long id)
{
this.id = id;
}
public Person setFirstName(String firstName)
{
this.firstName = firstName;
return this;
}
...
}
public static void main(String[] args)
{
Person mrBear = (new Person(1l)).setFirstName("B.").
setLastName("Bear").setTitle("Mr.");
}
Method Chaining does not break the Law of Demeter
[1]. It doesn't even talk to friends (in this case), but only to itself.
Here I have used a simplified example. Mostly you'd create a PersonBuilder to make Persons.
[4]
For some great uses of method chaining check out [2] and [3].
References
- [1] Glossary
- http://randomthoughtsonjavaprogramming.blogspot.nl/p/glossary.html
- [2] FluentInterface
- http://martinfowler.com/bliki/FluentInterface.html
- [3] Expression Builders
- http://martinfowler.com/bliki/ExpressionBuilder.html
- [4] Too Many Parameters in Java Methods, Part 3: Builder Pattern
- http://marxsoftware.blogspot.nl/2013/10/too-many-parameters-in-java-3-builder-pattern.html
