I have an array of hashes, @fathers.
a_father = { "father" => "Bob", "age" => 40 }
@fathers << a_father
a_father = { "father" => "David", "age" => 32 }
@fathers << a_father
a_father = { "father" => "Batman", "age" => 50 }
@fathers << a_father
How can I search this array and return an array of hashes for which a block returns true?
For example:
@fathers.some_method("age" > 35) #=> array containing the hashes of bob and batman
Thanks.
You're looking for Enumerable#select (also called find_all):
@fathers.select {|father| father["age"] > 35 }
# => [ { "age" => 40, "father" => "Bob" },
# { "age" => 50, "father" => "Batman" } ]
Per the documentation, it "returns an array containing all elements of [the enumerable, in this case @fathers] for which block is not false."
@fathers.find {|father| father["age"] > 35 } instead.
this will return first match
@fathers.detect {|f| f["age"] > 35 }
#select - But all goes for your use case. #detect will return nil if no match is found, while #select, in @Jordan's answer, will return [].
find instead of detect for a more readable code
find can get confusing in rails, however.
select and detect aren't same, select will transverse the whole array, while detect will stop as soon as the first match is found. IF you're looking for ONE match @fathers.select {|f| f["age"] > 35 }.first vs @fathers.detect {|f| f["age"] > 35 } for performance and readability, my vote goes for detectif your array looks like
array = [
{:name => "Hitesh" , :age => 27 , :place => "xyz"} ,
{:name => "John" , :age => 26 , :place => "xtz"} ,
{:name => "Anil" , :age => 26 , :place => "xsz"}
]
And you Want To know if some value is already present in your array. Use Find Method
array.find {|x| x[:name] == "Hitesh"}
This will return object if Hitesh is present in name otherwise return nil
"hitesh", it wont return the hash. How can we account for word casing as well in such cases?
array.any?{ |element| element[:name].casecmp("hitesh")==0 } should work for any case in start or anywhere in the string i.e. for "Hitesh", "hitesh" or "hiTeSh"
find is an alias for detect method(Adding to previous answers (hope that helps someone):)
Age is simpler but in case of string and with ignoring case:
@fathers.any? { |father| father[:name].casecmp("john") == 0 } should work for any case in start or anywhere in the string i.e. for "John", "john" or "JoHn" and so on.
@fathers.find { |father| father[:name].casecmp("john") == 0 }
@fathers.select { |father| father[:name].casecmp("john") == 0 }
The closest to @fathers.some_method("age" > 35) would be
@fathers.hselect("age", :>, 35)
← To enable this, one should evaluate the following
class TrueClass
def to_boolean
self
end
end
class FalseClass
def to_boolean
self
end
end
class Array
def to_boolean
!self.empty?
end
def select_criteria(field, op, val=nil)
-> ha{
if val.nil?
ha[field].send(op)
else
ha[field].send(op, val)
end.to_boolean}
end
def hop(method, field, op, val=nil)
self.send(method, &select_criteria(field, op, val))
end
def hselect(field, op, val=nil)
self.hop(:select, field, op, val)
end
def hreject(field, op, val=nil)
self.hop(:reject, field, op, val)
end
end
← where hreject is an example of another similar definition. More tricks are possible, for example:
@fathers << { "father" => "Sam", "age" => 44, "kids_ages" => [3, 8, 14] }
@fathers.hreject("kids_ages", :nil?)
@fathers.hselect("kids_ages", :&, [8])
@fathershash has a 'father' key rather than a 'name' key. I wish I could believe that those are the fathers' fathers, but I can't.