Contract
Return type	wob
No input parameters.
Parameter kind	Default value	Type
Other unkeyed arguments	opt

Water Contract
<method copy_down_data _other_unkeyed=opt=wob=ekind.code="_body"/>

See also: make

Used within an make method to easily copy down all the data fields of the class into the instance. It returns the modified _subject Data fields are fields whose value is not a method or a class.

<class foo x=5>
     <method make>
      .<copy_down_data/>
     </>
    </class>
<foo/>.<get "x"/>

Now all the instances of foo will have their own version of the field x. foo.<set x=99/> will not be seen by the foo instances since they now shadow the value in their parent. Note this is similar to many class-instance object systems wherein the instances always have their own copies of the instance variables. In Water, if an instance doesn't have a variable it looks up into its parent to get the value. If no field keys are explicitly given, only the field keys in _field_order of the parent are copied down. Fields that already exist in the subject are not copied down. To explicitly copy_down a field, give the field keys as arguments.

<class foo x=5 y=true z=integer>
     <method make>
      .<copy_down_data "z"/>
     </>
     <method bar/>
    </class>
<foo y=10/>

<foo x=5 y=10 z=number.integer/>