Class: DeclareSchema::Model::DeferredFieldSpec

Inherits:
Object
  • Object
show all
Defined in:
lib/declare_schema/model/deferred_field_spec.rb

Overview

A placeholder for a FieldSpec whose final shape can’t be computed at field- declaration time. The only producer today is ‘belongs_to` between two declare_schema models: we cannot touch `reflection.klass` while declaring the FK without risking a model-load cycle, so we stash an eager default-typed FieldSpec along with a block that knows how to mirror the parent’s PK once all models have been eager-loaded.

The migrator calls #resolve on every value in ‘field_specs` at the start of migration generation (see `Migrator#generate`); for plain FieldSpecs `#resolve` is a no-op returning self, while for instances of this class it invokes the block (memoized) with the default spec and returns the produced FieldSpec.

Instance Method Summary collapse

Constructor Details

#initialize(default_spec) {|default_spec| ... } ⇒ DeferredFieldSpec

Returns a new instance of DeferredFieldSpec.

Parameters:

  • default_spec (FieldSpec) —

    the eager placeholder spec

Yield Parameters:

Yield Returns:



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# File 'lib/declare_schema/model/deferred_field_spec.rb', line 21

def initialize(default_spec, &resolver)
  resolver or raise ArgumentError, "DeferredFieldSpec requires a resolver block"
  @default_spec = default_spec
  @resolver = resolver
end

Instance Method Details

#resolve ⇒ FieldSpec

Invoke the resolver block with the default spec and return its result. The migrator’s ‘transform_values!(&:resolve)` swaps this DeferredFieldSpec out of `field_specs` for the produced FieldSpec, so resolve is called exactly once per instance in production – no memoization needed.

Returns:



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# File 'lib/declare_schema/model/deferred_field_spec.rb', line 33

def resolve
  @resolver.call(@default_spec)
end