Class: ConvertSdk::Sentinel

Inherits:
Object
  • Object
show all
Defined in:
lib/convert_sdk/sentinel.rb

Overview

A frozen singleton sentinel — the SDK's public contract for a business miss.

Bucketing and feature decisions that find no answer (no data, not enough data, no variation decided) return a +Sentinel+ singleton rather than raising or returning a bare +nil+. This is architecture Decision 2: misses are signaled by value, never by exception.

The protocol a +Sentinel+ implements:

  • +#to_s+ — the byte-identical JS wire string (appears in payloads/logs).
  • +#key+ — always +nil+, so the documented integrator pattern +case variation&.key+ falls through to the +else+ branch on a miss.
  • +#error?+ — always +true+, the value-object discriminator that distinguishes a sentinel from a real BucketedVariation/BucketedFeature (both +false+).

Sentinels are exposed as frozen singleton constants (e.g. RuleError::NO_DATA_FOUND), so callers can branch on object identity for granular handling:

result = context.run_experience("homepage-test") case result.key when nil # a miss — inspect which one via identity show_default if result.equal?(ConvertSdk::RuleError::NO_DATA_FOUND) else render_variation(result.key) end

Equality is intentionally left as default object identity (no +==+ override): two distinct +Sentinel+ instances built from the same wire string are NOT equal, which is why the canonical instances live as shared frozen constants.

Instance Method Summary collapse

Constructor Details

#initialize(wire_string) ⇒ Sentinel

Returns a new instance of Sentinel.

Parameters:

  • wire_string (String) —

    the JS-parity wire string this sentinel emits.



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# File 'lib/convert_sdk/sentinel.rb', line 37

def initialize(wire_string)
  @wire_string = wire_string.dup.freeze
  freeze
end

Instance Method Details

#error? ⇒ Boolean

Returns always true — a sentinel always signals a business miss.

Returns:

  • (Boolean) —

    always true — a sentinel always signals a business miss.



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# File 'lib/convert_sdk/sentinel.rb', line 53

def error?
  true
end

#key ⇒ nil

Returns always nil, so +case variation&.key+ falls through to else.

Returns:

  • (nil) —

    always nil, so +case variation&.key+ falls through to else.



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# File 'lib/convert_sdk/sentinel.rb', line 48

def key
  nil
end

#to_s ⇒ String

Returns the byte-identical JS wire string.

Returns:

  • (String) —

    the byte-identical JS wire string.



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# File 'lib/convert_sdk/sentinel.rb', line 43

def to_s
  @wire_string
end