SQL-like syntax for array of objects - ruby-on-rails

Question

I have an array of objects. I need to use an SQL-like condition WHERE field like '%value%' for some object fields in this array.
How to do it?
Edited:
For example I have array with Users and I need to find all users with first_name like ike and email like 123.
Edited2:
I need method to get Users with first_name like smth and email like smth from ARRAY of my Users. Users have first_name and email.
Edited3:
All my users are in database. But I have some business logic, at the end of this logic I have array with Users. Next I need to filter this array with some text: ike for first_name and 123 for email. How to do it?

Answer 1

arr = %w[hello quick bool boo foo]
arr.select { |x| x.include?("foo") }
=> ["bool", "boo", "foo"]
or in your case, if you have an array of objects, you can do:
x.first_name.include?("foo") && x.email.include?("123")
For more customization, you can use Array#select with Regexeps

Answer 2

If you can just use ruby methods for this that do something like this:
User = Struct.new(:email, :first_name) # Just creating a cheap User class here
users = [
User.new('1#a.com' , 'ike'),
User.new('123#a.com', 'bob'),
User.new('123#a.com', 'ike'),
]
# results will be an array holding only the last element in users
results = users.find_all do |user|
user.email =~ /123/ and
user.first_name =~ /ike/
end
Writing your own sql parser seems like a pretty bad idea, but if you really need to parse simple SQL where clauses you could do something like this:
User = Struct.new(:email, :first_name) # Just creating a cheap User class here
users = [
User.new('1#a.com' , 'ike'),
User.new('123#a.com', 'bob'),
User.new('123#a.com', 'ike'),
]
def where(array, sql)
sql = sql.gsub(/\s+AND\s+/, ' ') # remove AND's
terms = Hash[ *sql.split(/\s+LIKE\s+| /) ] # turn "a LIKE 'b'" into {'a': "'b'"}
array.find_all do |item|
terms.all? do |attribute, matcher|
matcher = matcher.gsub('%', '.*') # convert %
matcher = matcher.gsub(/^['"]|["']$/, '') # strip quotes
item.send(attribute) =~ /^#{matcher}$/
end
end
end
# results will be an array holding only the last element in users
results = where(users, "first_name LIKE '%ike%' AND email LIKE '%123%'")
This will only work for where clauses what only contain LIKE statements connected by AND's. Adding support for all valid SQL is left as an exercise for the reader, (or better yet, just left alone).

Answer 3

I've built a ruby gem uber_array to enable sql-like syntax for arrays of Hashes or Objects you might want to try.
require 'uber_array'
# Array of Hash elements with strings as keys
items = [
{ 'name' => 'Jack', 'score' => 999, 'active' => false },
{ 'name' => 'Jake', 'score' => 888, 'active' => true },
{ 'name' => 'John', 'score' => 777, 'active' => true }
]
uber_items = UberArray.new(items)
uber_items.where('name' => 'John')
uber_items.where('name' => /Ja/i)
uber_items.like('ja')
uber_items.where('name' => %w(Dave John Tom))
uber_items.where('score' => 999)
uber_items.where('score' => ->(s){s > 900})
uber_items.where('active' => true, 'score' => 800..900)