Module: Tablesmith

Defined in:
lib/tablesmith/table.rb,
lib/tablesmith/version.rb,
lib/tablesmith/delegated_array_class.rb

Defined Under Namespace

Modules: ActiveRecordSource, ArrayRowsSource, HashRowsBase, HashRowsSource Classes: Column, Table

Constant Summary collapse

VERSION = 
'0.7.0'

Class Method Summary collapse

Class Method Details

.delegated_array_class ⇒ Object

This adjustment to ‘DelegateClass(Array)` is necessary to allow calling puts on a `Tablesmith::Table` and still get the table output, rather than the default puts output of the underlying `Array`.

Explaining why requires breaking some things down.

The implementation of ‘Kernel::puts` has special code for an `Array`. The code inside `rb_io_puts` (in io.c) first checks to see if the object passed to it is a `String`. If not, it then calls `io_puts_ary`, which in turn calls `rb_check_array_type`. If `rb_check_array_type` confirms the passed object is an `Array`, then `io_puts_ary` loops over the elements of the `Array` and passes it to `rb_io_puts`. If the `Array` check fails in the original `rb_io_puts`, `rb_obj_as_string` is used.

Early versions of ‘Tablesmith::Table` subclassed `Array`, but even after changing `Tablesmith::Table` to use any of the `Delegator` options, the code in `rb_check_array_type` still detected `Tablesmith::Table` as an `Array`. How does it do this?

‘rb_check_array_type` calls:

`return rb_check_convert_type_with_id(ary, T_ARRAY, "Array", idTo_ary);`

If a straight up type check fails, then it attempts to convert the object to an ‘Array` via the `to_ary` method.

And wha-lah. We simply need to undefine the ‘to_ary` method added to `Tablesmith::Table` by `DelegateClass(Array)` and `rb_io_puts` will no longer output `Table` as an `Array` and will use its `to_s` method, the same as `print`.



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# File 'lib/tablesmith/delegated_array_class.rb', line 36

def self.delegated_array_class
  DelegateClass(Array).tap do |klass|
    klass.undef_method(:to_ary)
  end
end