Why is the new method not needed for creating Rational in ruby

Question

Possible Duplicate:
Ruby syntax question: Rational(a, b) and Rational.new!(a, b)

I'm in the process of reading the ruby pickaxe book, and I'm confused about the syntax of creating rational numbers.

Rational(3,4) * Rational(1,2)

produces

=> 3/8

Why is the new method not needed for Rational (I also noticed for example I can create a string without the new method)?

Ah yes, I didn't see that duplicate. You are correct. – Jeff Storey Jun 27 '12 at 00:37 — Jeff Storey, Jun 27 '12 at 00:37

score 6 · Accepted Answer · edited May 23 '17 at 11:48

6

For one thing, Ruby has no new keyword. new is a class method that all classes have (they inherit it from Class) that creates an object of that class. When you see something like Rational(3,4), Rational is really just a private method of Object (defined in Kernel) that makes creating rational numbers easier. For more on those constructor-methods, see this answer of mine: https://stackoverflow.com/a/9677125/1008938

edited May 23 '17 at 11:48

Community

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answered Jun 27 '12 at 00:36

Linuxios

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Thanks yes, sorry I meant the new method. – Jeff Storey Jun 27 '12 at 00:37
@JeffStorey: Oh. But the rest of the answer still holds. And take a look at that link. – Linuxios Jun 27 '12 at 00:37

score 3 · Answer 2 · answered Jun 27 '12 at 00:36

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It's a method that happens to have the same name as the class. It's a common conversion idiom in Ruby.

answered Jun 27 '12 at 00:36

jmdeldin

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Thanks. Good to pick up these common ruby idioms as I'm learning rather than just learning the syntax. – Jeff Storey Jun 27 '12 at 00:40

Why is the new method not needed for creating Rational in ruby

2 Answers2