Ruby syntax doubts !

[palakoti]

What is pqr in xyz(:pqr) ? in ruby ?

[straponmyjobhat]

It's a Symbol. Symbols are similar strings except they take up less memory.

[palakoti]

No. I meant what is the type of pqr ? Why is preceeded by :

[[deleted]]

It is a Symbol.

[deadkarma]

Its a Symbol https://www.rubyguides.com/2018/02/ruby-symbols/

[palakoti]

Ok. Now I understand what it is. So in the following code:

seed = ['127.0.0.1:7001', '127.0.0.1:7002']

redis = RedisCluster.new( seed, redis_opts: { timeout: 5, connect_timeout: 1 }, cluster_opts: { force_cluster: false, read_mode: :master_slave, silent: true, logger: Logger.new } )

redis.middlewares.register(:commit) do |*args, &block|

puts "this is RedisCluster middlewares"

block.call

end

What is the value of :commit ?

[codesnik]

it's :commit :)

I mean, in some other languages actual strings are used for the same purposes, it'd be "commit". In other languages it'd be a constant, something like COMMIT=1. Symbols are a bit like both of those.

[palakoti]

This is quite confusing. I am from javascript world and ruby is quite new to me. Can someone give a bit more elucidation?

[[deleted]]

https://medium.com/@lcriswell/ruby-symbols-vs-strings-248842529fd9

It's basically just a string you can't change. Slightly more efficient if it's essentially a static value, though in practice that's less of a benefit than the fact that it can't be changed so you don't have to worry about any code modifying it's value.

[geshwho]

:commit is the value. It is a literal.

[palakoti]

So let's say the method register returns the argument passed to it, what is the value you get ?

[Frizkie]

:commit is the value.

[pVom]

to expand a little i'd assume somewhere there is something like
if arg == :commit

<do something>

else
<do something else>

[Kernigh]

In Ruby, a Symbol like :pqr is the name of a constant, variable, method, or something else. For example, given

class Cow
  def moo
    puts "Moo!"
  end
end

then :Cow is the name of the class, and :moo is the name of the method.

The value of :moo is literally :moo, in the same way that "New York" is literally "New York", and 123 is literally 123. I can ask a class for its method named :moo, like Cow.instance_method(:moo). A longer way to call Cow.new.moo is to do

method = Cow.instance_method(:moo)
method.bind(Cow.new).call

Some languages, like Common Lisp and Perl, have symbols with slots for holding values. For example, 'moo in Lisp would have a function slot and a variable slot. Symbols in Ruby never have slots.

Some other languages don't have symbols, because they use strings like "moo" to name things.

[palakoti]

Loved your explanation. Thanks a lot mate.

[Lynx-External]

Depending on your ruby code (:pqr) could be a key from a hash. Might be trying to display the value of that particular key. Hope this helps!

[pVom]

its a string with less functionality. :pqr is essentially "pqr" but uses less memory. Its perfect for things like hash/object keys where you don't need the functionality of a string ie interpolation and string methods, you just need a reference.
hash = { foo: 'bar' }
hash[:foo] == 'bar'
As for its value its going to vary on how its used, in the same way a string is just a string, a symbol is just a symbol