How are values cast when assigning to a Boolean field in Rails ActiveRecord? -

short version of question

in rails activerecord, if have boolean field , assign "abc" or 2, gets cast false. value 1 cast true, , nil remains nil. why case? can find rails documentation (or ruby documentation) explains behavior?

long version of question

i having difficulty understanding how rails handles attempts assign values boolean field in rails model. example, let's have website model has string field called :domain , boolean field called :can_ssl.

my migration looks this:

class createwebsites < activerecord::migration   def change     create_table :websites |t|       t.string :domain       t.boolean :can_ssl, :default => false        t.timestamps     end   end end 

in model file, add validation rules, looks this:

class website < activerecord::base   validates :domain, :presence => true   validates :can_ssl, :inclusion =>  { :in => [true, false] } end 

simple enough. based on i've done, i'm expecting :can_ssl can set values true or false, , nothing else. else result in valid? being false.

but once start playing around in console, notice that, actual assignment statement, value provide being recast true or false (or nil). rules governing how value gets cast boolean?

examples console:

w = website.new w.domain = 'stackoverflow.com' w.can_ssl = true w.can_ssl    # => true w.valid?     # => true  w.can_ssl = nil w.can_ssl    # => nil w.valid?     # => false (so far good)  w.can_ssl = 'abc' w.can_ssl    # => false (how did 'abc' become value false?) w.valid?     # => true  w.can_ssl = 1 w.can_ssl    # => true (i guess makes sense 1 casts true) w.valid?     # => true  w.can_ssl = 2 w.can_ssl    # => false (but other 1 casts false?) w.valid?     # => true 

so, based on i've done far, think can conclude following:

• when assigning value 1 or true boolean field, value cast true , assigned.
• when assigning nil boolean field, field assigned nil.
• when assigning else (such string or number not 1), value cast false.

am understanding correctly? missing anything?

i'm having difficulty finding documentation boolean field type in rails can give me clarification on this.

this done in bowels of activerecord: with

activerecord::connectionadapters::column.value_to_boolean 

at least in version of rails (it may somewhere different in more recent versions).

here's source in version

    # file activerecord/lib/active_record/connection_adapters/abstract/schema_definitions.rb, line 144     144:         def value_to_boolean(value)     145:           if value.is_a?(string) && value.blank?     146:             nil     147:           else     148:             true_values.include?(value)     149:           end     150:         end 

where true_values defined

#activerecord/lib/active_record/connection_adapters/abstract/schema_definitions.rb:10:       true_values = [true, 1, '1', 't', 't', 'true', 'true'].to_set 

1, 0, "f" , "t" there because of popular dbms's mysql & postgresql, store bools 0/1 , "f"/"t" respectively.

it's worth noting difference between , passes "if" test in ruby/rails, ie values "truthy" or "falsy" ("falsy" values fail if test, "truthy" values pass it).

in ruby, nil , false "falsy" , literally anything else (including 0, empty arrays, empty strings, empty hashes etc) "truthy". so, there's massive disparity between deemed truthy/falsy in ruby , saved true/false boolean database column.