Dumb question: in documentation, why Object#method, and not

Ruby
1

I keep seeing this syntax in documentation: Object#method, but in actual
use sending a message to an object is usually

    object = Object.new
    object.method

Is this just to emphasize that method() operates on an instance of
Object and not the class Object?

            Elf
2

On Thu, Dec 01, 2005 at 04:17:30AM +0900, Elf M. Sternberg wrote:

I keep seeing this syntax in documentation: Object#method, but in actual
use sending a message to an object is usually

    object = Object.new
    object.method

Is this just to emphasize that method() operates on an instance of
Object and not the class Object?

The # is a naming convention.

Class#method means method is an instance method.
Class::method means method is a class method.

For example, do

ri IO.read

There is IO::read and IO#read.

marcel

3

Elf M. Sternberg wrote:

I keep seeing this syntax in documentation: Object#method, but in actual
use sending a message to an object is usually

    object = Object.new
    object.method

Is this just to emphasize that method() operates on an instance of
Object and not the class Object?

Yes.

4

Elf M. Sternberg wrote:

I keep seeing this syntax in documentation: Object#method, but in actual
use sending a message to an object is usually

    object = Object.new
    object.method

Is this just to emphasize that method() operates on an instance of
Object and not the class Object?

Yes.

5

Yes. :wink:

6

On 11/30/05, Elf M. Sternberg [email protected] wrote:

I keep seeing this syntax in documentation: Object#method, but in actual
use sending a message to an object is usually

    object = Object.new
    object.method

Is this just to emphasize that method() operates on an instance of
Object and not the class Object?

As others have said, yes. As I understand it, though, it’s a
smalltalkism.

-austin

7

Notice that “Object” in “Object#method” is capitalized. We’re talking
about a class here not an instance. So if you were to say Object.method
you’d be refering to an instance method of the class itself --generally
called a class method, as opposed to an instance method defined by
the class. It’s tricky because its relative --a class is itself an
instance of Class.

HTH,
T.

8

David A. Black wrote:

ri IO.read

There is IO::read and IO#read.

Interesting – I never picked up on ri’s use of :: in preference to
the dot. I personally use Class.method for class methods (indeed for
any singleton method).

I believe that to be the convention, too.

Klass.method <- Class method
Klass#method <- Instance method
Klass::FOO <- Class constant
Klass::AnotherKlass <- Class constant (class or module)

9

Hi –

On Thu, 1 Dec 2005, Marcel Molina Jr. wrote:

The # is a naming convention.

Class#method means method is an instance method.
Class::method means method is a class method.

For example, do

ri IO.read

There is IO::read and IO#read.

Interesting – I never picked up on ri’s use of :: in preference to
the dot. I personally use Class.method for class methods (indeed for
any singleton method).

David

10

On Fri, 2005-12-02 at 00:37 +0900, jwesley wrote:

Hmm…so Class is an instance of itself?

Yep.

Class.class # => Class

-mental

11

Hi –

On Fri, 2 Dec 2005, jwesley wrote:

Hmm…so Class is an instance of itself?

Yes. And Object is a Class, and Class is an Object :slight_smile: Ruby
object-space chases its own tail a bit at the top of the hierarchy,
for the sake of bootstrapping itself into existence.

David

12

Hmm…so Class is an instance of itself?

13

2009/7/28 Gary L. [email protected]

            Elf

Where is this documented? I can’t find it in any book…and searching
google on Ruby object#method doesn’t lead to an explanation of this. You
get reams of hits using object#method syntax but not where it comes
from.

http://ruby-doc.org/core/classes/Object.html#M000336

14

Where is this documented? I can’t find it in any book…and searching
google on Ruby object#method doesn’t lead to an explanation of this.

I immediately found it on ruby-doc.org:
class Object - RDoc Documentation

Regards
Nicolai

15

Nicolai Reuschling wrote:

Where is this documented? I can’t find it in any book…and searching
google on Ruby object#method doesn’t lead to an explanation of this.

I immediately found it on ruby-doc.org:
class Object - RDoc Documentation

Regards
Nicolai

Thanks for taking the time, I suspect I didn’t make my question
clear,there is nothing that I can see on the link Object.html#M000336
that specifies what object#method means vs object::method but your link
lead me to search on the site and I found it here
Ruby Documentation Submission Guidelines, somewhat buried but
certainly clear.

Style Guidelines

Use :: for describing class methods,
# for describing instance methods,
. for example code.

16

Gary L. schrieb:

            Elf

Where is this documented? I can’t find it in any book…and searching
google on Ruby object#method doesn’t lead to an explanation of this. You
get reams of hits using object#method syntax but not where it comes
from.

The 1st edition of "Programming Ruby"1 (a.k.a. the “Pickaxe”) mentions
this notation:

Within the text, Fred#doIt is a reference to an instance method (doIt) of
class Fred, while Fred.new [In some other Ruby documentation, you may
see class methods written as Fred::new. This is perfectly valid Ruby
syntax; we just happen to feel that Fred.new is less distracting to
read.] is a class method, and Fred::EOF is a class constant.

The first appearance in the Ruby changelog2 dates back to 1995,
suggesting that Matz himself may have introduced this convention.

-Matthias

17

elf wrote:

I keep seeing this syntax in documentation: Object#method, but in actual
use sending a message to an object is usually

    object = Object.new
    object.method

Is this just to emphasize that method() operates on an instance of
Object and not the class Object?

            Elf

Where is this documented? I can’t find it in any book…and searching
google on Ruby object#method doesn’t lead to an explanation of this. You
get reams of hits using object#method syntax but not where it comes
from.