Can't understand for this each

Ruby
1

Hello,

Please take a look at below.
what’s each{ … } in the find_all method?
I can’t understand for it. thanks.

class Hash
def find_all
new_hash = Hash.new
each { |k,v| new_hash[k] = v if yield(k, v) }
new_hash
end
end

squares = {0=>0, 1=>1, 2=>4, 3=>9}
z=squares.find_all { |key, value| key > 1 }
p z

2

On Sat, Jan 2, 2010 at 6:20 AM, Ruby N. [email protected]
wrote:

new_hash
end
end

squares = {0=>0, 1=>1, 2=>4, 3=>9}
z=squares.find_all { |key, value| key > 1 }
p z

An English translation might read “For each key value pair in the hash,
add
it to the new hash if the block submitted returns true.”

3

Hi,

Am Samstag, 02. Jan 2010, 21:20:02 +0900 schrieb Ruby N.:

what’s each{ … } in the find_all method?

class Hash
def find_all
new_hash = Hash.new
each { |k,v| new_hash[k] = v if yield(k, v) }
new_hash
end
end

Hash#each' is not Array#each’. It is descibed in
http://www.ruby-doc.org/docs/ProgrammingRuby/html/ref_c_hash.html#Hash.each.

It does something like

class Hash
def each
keys.each { |k|
yield k, self[ k]
}
end
end

A remarkable aspect is that `Hash#each’ yields two values so that
everywhere in Enumerable’s descriptions “{ |obj| … }” has to be
replaced with “{ |k,v| … }” or even “|(k,v)|”. For example, you
have to call

hash.each_with_index { |(k,v),i| … }

Bertram

4

On Sun, Jan 3, 2010 at 2:36 AM, Brian C. [email protected]
wrote:

Ruby N. wrote:

Hello,

Please take a look at below.
what’s each{ … } in the find_all method?
I can’t understand for it. thanks.

Would it help if you think of it as “self.each” ?

oops that’s right.
I know what’s each.
But I don’t understand for a raw each there…
yes self.each, got it, thanks!

Jenn.

5

Ruby N. wrote:

Hello,

Please take a look at below.
what’s each{ … } in the find_all method?
I can’t understand for it. thanks.

Would it help if you think of it as “self.each” ?

That is, you are calling the method called “each” on the current object
instance, which in this case is a Hash.