SLB: Notes – File Loading: Context & Callbacks

By Sol in Lab


  1. Conditional use of callback (based on context)
    • Only run callback if associated context is valid
  2. Global use of callback (regardless of context)


  • Callbacks are always assumed to be internal methods of calling instance object, thus callbacks are defined as a string (method name)
    • 'callback-name' set to $this->callback-name() when parsed

Methodology (Options)

  1. Pair context/callback
    • Conditional callback
      • Defined in context property
      • Context only: (string) 'context-name'
      • Context + Callback: (array) ['context-name', 'callback']
    • Global callback
      • Defined in callback property
    • + Clearly separated functionality (conditional vs. global)
    • + Allows global & conditional callbacks simultaneously (global callback and context/callback pair will be evaluated if set)
    • - Ambiguous – Multiple contexts are grouped in an array & context/callback pairs are also grouped in an array
      • Issue when single context specified (single context does not currently need to be placed in an array)
      • Options
        1. Mandatory wrapping of contexts in array
          • context property is always an array
          • + Consistent: No chance for confusion
          • - Extra work: must always create array
          • + Strict specification: No edge cases
  2. Context/Callback in separate properties, but matching
    • e.g. 1st context matches 1st callback, etc.
    • context property: (array) ['context-1', 'context-2', 'context-3']
    • callback property: (array) ['callback-1', null, 'callback-3']
    • Pairs (context/callback): context-1/callback-1, context-2/(no callback), context-3/callback-3
    • ? Global callback?
      • - callback property populated with conditional callbacks
    • ? Context without callback?
      • Set null at matching index in callback array
    • - Must always keep callbacks/contexts matched up
  3. Context/Callback pair defined as string
    • Similar to 1 but using delimiter to separate context & callback
    • Example: 'context-name|callback-name' (pipe character is delimiter)
    • + Simple to implement: No need to add arrays, etc.
    • + Less to type: just delimiter
    • - More prone to errors: Since values are not separated by array
    • ? Less strict specification than 1 good or bad?
      • - Must keep track of delimiter character
        • Array is specific/consistent, while delimiter character may be changed (error if new delimiter is not propagated throughout code)