Determining type of an object in ruby

Question

I\'ll use python as an example of what I\'m looking for (you can think of it as pseudocode if you don\'t know Python):

>>> a = 1
>>> type(a)
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Answer 1

you could also try: instance_of?

p 1.instance_of? Fixnum    #=> True
p "1".instance_of? String  #=> True
p [1,2].instance_of? Array #=> True

Answer 2

Oftentimes in Ruby, you don't actually care what the object's class is, per se, you just care that it responds to a certain method. This is known as Duck Typing and you'll see it in all sorts of Ruby codebases.

So in many (if not most) cases, its best to use Duck Typing using #respond_to?(method):

object.respond_to?(:to_i)

Answer 3

I would say "Yes". As "Matz" had said something like this in one of his talks, "Ruby objects have no types." Not all of it but the part that he is trying to get across to us. Why would anyone have said "Everything is an Object" then? To add he said "Data has Types not objects".

So we might enjoy this.

https://www.youtube.com/watch?v=1l3U1X3z0CE

But Ruby doesn't care to much about the type of object just the class. We use classes not types. All data then has a class.

12345.class

'my string'.class

They may also have ancestors

Object.ancestors

They also have meta classes but I'll save you the details on that.

Once you know the class then you'll be able to lookup what methods you may use for it. That's where the "data type" is needed. If you really want to get into details the look up...

"The Ruby Object Model"

This is the term used for how Ruby handles objects. It's all internal so you don't really see much of this but it's nice to know. But that's another topic.

Yes! The class is the data type. Objects have classes and data has types. So if you know about data bases then you know there are only a finite set of types.

text blocks numbers

Answer 4

variable_name.class

Here variable name is "a" a.class

Answer 5

The proper way to determine the "type" of an object, which is a wobbly term in the Ruby world, is to call object.class.

Since classes can inherit from other classes, if you want to determine if an object is "of a particular type" you might call object.is_a?(ClassName) to see if object is of type ClassName or derived from it.

Normally type checking is not done in Ruby, but instead objects are assessed based on their ability to respond to particular methods, commonly called "Duck typing". In other words, if it responds to the methods you want, there's no reason to be particular about the type.

For example, object.is_a?(String) is too rigid since another class might implement methods that convert it into a string, or make it behave identically to how String behaves. object.respond_to?(:to_s) would be a better way to test that the object in question does what you want.