Class: StrictLazy::Loader

Inherits:
Object
  • Object
show all
Defined in:
lib/strict_lazy/loader.rb

Overview

Immutable definition produced by a lazy_load declaration.

It holds the reader name, the resolver (a from: method symbol or a block), whether resolution is eager (sync:), and the default used for records the resolver does not fulfill.

Resolution always goes through #resolve, which is handed the model class so a from: symbol can be dispatched as a class method. A block resolver is instance_exec‘d on the model class for the same lookup semantics.

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(reader:, sync:, default:, from: nil, block: nil) ⇒ Loader

Returns a new instance of Loader.



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# File 'lib/strict_lazy/loader.rb', line 18

def initialize(reader:, sync:, default:, from: nil, block: nil)
  @reader = reader
  @sync = sync
  @default = default
  @from = from
  @block = block
  # The ivar name may not contain `?`, so a predicate reader is encoded
  # (not stripped): +commented?+ and +commented+ get distinct ivars. (A bare
  # reader literally named +commented_pred+ would collide, but reader names
  # are validated to a bare-name/`?` form, making that pairing a non-idiom.)
  ivar_key = reader.to_s.sub(/\?\z/, "_pred")
  @value_ivar = :"@_lazy_#{ivar_key}"
  @batch_ivar = :"@_batch_#{ivar_key}"
end

Instance Attribute Details

#batch_ivar ⇒ Object (readonly)

Returns the value of attribute batch_ivar.



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# File 'lib/strict_lazy/loader.rb', line 35

def batch_ivar
  @batch_ivar
end

#default ⇒ Object (readonly)

Internal ivar names are reserved per reader: @lazy<reader> holds the resolved value, @batch<reader> holds the shared Batch reference.



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# File 'lib/strict_lazy/loader.rb', line 16

def default
  @default
end

#reader ⇒ Object (readonly)

Internal ivar names are reserved per reader: @lazy<reader> holds the resolved value, @batch<reader> holds the shared Batch reference.



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# File 'lib/strict_lazy/loader.rb', line 16

def reader
  @reader
end

#sync ⇒ Object (readonly)

Internal ivar names are reserved per reader: @lazy<reader> holds the resolved value, @batch<reader> holds the shared Batch reference.



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# File 'lib/strict_lazy/loader.rb', line 16

def sync
  @sync
end

#value_ivar ⇒ Object (readonly)

Returns the value of attribute value_ivar.



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# File 'lib/strict_lazy/loader.rb', line 35

def value_ivar
  @value_ivar
end

Instance Method Details

#default_for(record) ⇒ Object

Compute the default for a record the resolver did not fulfill. A callable default acts as a per-record factory so mutable values ([], {}) are never shared; arity 1 receives the record.



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# File 'lib/strict_lazy/loader.rb', line 50

def default_for(record)
  return @default unless @default.respond_to?(:call)

  @default.arity.zero? ? @default.call : @default.call(record)
end

#resolve(model, records, loader) ⇒ Object

Invoke the resolver once over records. loader is the loader.call(record, value) callable supplied by the Batch.



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# File 'lib/strict_lazy/loader.rb', line 39

def resolve(model, records, loader)
  if @from
    model.public_send(@from, records, loader)
  else
    model.instance_exec(records, loader, &@block)
  end
end

#sync? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/strict_lazy/loader.rb', line 33

def sync? = @sync