Class: Parse::Constraint::ArrayEmptyConstraint

Inherits:

Parse::Constraint

• Object
• Parse::Constraint
• Parse::Constraint::ArrayEmptyConstraint

Defined in:

lib/parse/query/constraints.rb

Overview

Note:

This uses the arr_empty name to avoid conflict with the existing empty constraint which checks if the first array element exists.

Note:

The true case uses equality which can leverage MongoDB indexes. The false case still requires $size which cannot use indexes.

Array empty constraint - matches arrays with no elements. Uses direct equality for the true case (index-friendly) rather than $size.

q.where :tags.arr_empty => true   # arrays with 0 elements (uses { field: [] })
q.where :tags.arr_empty => false  # arrays with 1+ elements (uses $size > 0)

See Also:

• ArraySizeConstraint
• ArrayNotEmptyConstraint
• ArrayEmptyOrNilConstraint

Instance Attribute Summary

Attributes inherited from Parse::Constraint

#operand, #operation, #operator, #value

Instance Method Summary

• #arr_empty ⇒ ArrayEmptyConstraint

  A registered method on a symbol to create the constraint.

• #build ⇒ Hash

  The compiled constraint using aggregation pipeline.

Methods inherited from Parse::Constraint

#as_json, constraint_keyword, create, formatted_value, #formatted_value, #initialize, #key, #precedence, register, #to_s

Constructor Details

This class inherits a constructor from Parse::Constraint

Instance Method Details

#arr_empty ⇒ ArrayEmptyConstraint

A registered method on a symbol to create the constraint.

Examples:

q.where :field.arr_empty => true

Returns:

• (ArrayEmptyConstraint)

# File 'lib/parse/query/constraints.rb', line 622

register :arr_empty

#build ⇒ Hash

Returns the compiled constraint using aggregation pipeline.

Returns:

• (Hash) —

  the compiled constraint using aggregation pipeline.

# File 'lib/parse/query/constraints.rb', line 625

def build
  value = formatted_value
  unless value == true || value == false
    raise ArgumentError, "#{self.class}: Value must be true or false"
  end

  field_name = Parse::Query.format_field(@operation.operand)

  if value
    # Use direct equality for empty array (can use MongoDB index)
    pipeline = [{ "$match" => { field_name => [] } }]
  else
    # For non-empty, use $ne [] which is index-friendly
    # Note: This matches arrays with elements but also matches nil/missing
    # Use not_empty constraint if you need to exclude nil/missing
    pipeline = [{ "$match" => { field_name => { "$ne" => [] } } }]
  end

  { "__aggregation_pipeline" => pipeline }
end