What does the construction -> {} mean?

Question

ruby

Hey! I often see the design (arg) -> {}
I Know Coffee and there it denotes a function. However, a = (arg) -> { 920 }it doesn’t work :(
I googled it, but I didn’t find an answer. So, what does this construction mean?
The most interesting thing is that you have to use it yourself, without even understanding its meaning.

Answer 1

It's a lambda (or proc )
In short, at its core, it's a callable object. Where you store an arbitrary block with arbitrary formal variables. And at any time you have the opportunity to call a method on itcall

a = -> { |time| User.where(created_at: time) }
...
a.call(Time.now)

When the brackets are before the lambda, it's just that the syntax is different