Procer
A reasonable good default to_proc
method for all objects.
Install with:
gem install procer
Whe you require Procer, all objects will have a default to_proc
method which will try to call one of the following methods, in the
given order:
call
[]
===
Many methods which receive a block, can benefit greatlly from this because you can now pass an object to perform the block role.
Think of the Enumerable module and all it's methods.
Many objects define ===
, but not to_proc
. So they will be nicelly
usable in a case/when
expression, but not in other contexts.
This is the case of classes and ranges, which you can use in
case/when
expressions, but they don't define to_proc
.
Now they do define to_proc
so they are useful in those contexts.
Examples:
require 'procer'
[1, 2, '3', '4', 5, 6].filter(&Numeric)
# => [1, 2, 5, 6]
[-10, 100, -2, 3, 20, -33].filter(&(0..50))
# => [3, 20]
Also, Hashes already implement to_proc
and that is really useful
with enumerator. We can use it as a transformation table with map
:
table = {
1 => 'one',
2 => 'two',
3 => 'three'
}
[3, 1, 2].map(&table)
# => ['three, 'one, 'two']
Sadly, Arrays, even when they have the same interface as hashes as a
function of indices, don't implement to_proc
and so they can't be used
in the same way. Until now.
table = ['zero', 'one', 'two']
[2, 0, 1].map(&table)
# => ['two', 'zero', 'one']
Alternativaly you could have use values_at
:
table.values_at([3, 1, 2]) # In the Hash example
table.values_at([2, 0, 1]) # In the Array example
But the map solution is more generic and table
can be anything that
implements to_proc
and not something that necesarilly implement
values_at
.
Notice that if the object implements []
that will triumph over
===
. It was unexpected when I tried to use Integers as the object, as
they implement []
as a way to access it's binary form:
5 # b101
[5[2], 5[1], 5[0]] # [1, 0, 1]
So the proc will work like that:
[2, 4, 5].map(&5)
# Actual => [1, 0, 0]
# I was expecting => [false, false, true]