Tuesday, December 18, 2007
The beauty of return this;
As a beginner I was fascinated by the repeated append calls on the StringBuffer (Java) object. Especially because of the saving in the typing and no more string concatenation.
This time more than typing benefit what I liked about it is the readability of thecode. This is very close to the natural language translation of the above.
"Expect a method call someMethod on someObj. someMethod returns anotherObject. someMethod call is expected only once." Isn't that very close to how the code reads itself?
new StringBuffer("start").append("more").append("more")Obviously the return statement of the append method should look likereturn this;
Later I came across more interesting examples of this in the mock libraries like below.
Expect.Call(someObj.someMethod()).Return(anotherObject).Repeat().Once();This time more than typing benefit what I liked about it is the readability of thecode. This is very close to the natural language translation of the above.
"Expect a method call someMethod on someObj. someMethod returns anotherObject. someMethod call is expected only once." Isn't that very close to how the code reads itself?
Look at this now."Create a new bug on build 45576 with description "this is really bugging ....". new Bug("new one").onBuild(45576).withDescription("this is really bugging")
.WithPriority("medium").reportedBy("QA")and this bug = new Bug("new one"); bug.setDescription("...."); bug.setBuild(45576)......We can improve the readability by adding 'And', 'With', 'To' etc.Below I have added a creational method and used 'and' method toimprove the readability a bit more.
Bug.CreateWithTitle("new one").onBuild(45576) .withDescription("this is really bugging")¶ 11:21 PM.WithPriority("medium").reportedBy("QA").and().assignTo("a dev")...
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Thank you for the reference. Is this the URL (http://martinfowler.com/dslwip/)? The page is not found. do you know about any alternate sources for the same.
Is method chaining specific to DSL?(sorry I am not familiar with DSL)
Is method chaining specific to DSL?(sorry I am not familiar with DSL)
Method Chaining is a way of implementing DSLs (like JMock does) or Fluent Interfaces. Martin's book draft has a lot of information (the URI you wrote is correct), althouh I sightly disagree with him.
Other text about those language adaptations:
http://fragmental.tw/research-on-dsls/language-adaption/
But method chaining is not used only for this, languages like Smalltalk uses this all the time without creating a new or specialized language.
Cheers
Phillip Calçado
http://fragmental.tw
Other text about those language adaptations:
http://fragmental.tw/research-on-dsls/language-adaption/
But method chaining is not used only for this, languages like Smalltalk uses this all the time without creating a new or specialized language.
Cheers
Phillip Calçado
http://fragmental.tw
Returning 'this' that lets developers chain method calls takes a lot of java developer by surprise.
This has always been a convention in smalltalk, and is one reason why smalltalk code is beautiful, and the code talks to you.
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This has always been a convention in smalltalk, and is one reason why smalltalk code is beautiful, and the code talks to you.
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