# oometa(3tcl) 0.7.2 oometa "Data registry for TclOO frameworks"

## Name

oometa - oo::meta A data registry for classess

## Synopsis

- oo::meta::info
- oo::meta::info branchget ?key? ?...?
- oo::meta::info branchset ?key...? key value
- oo::meta::info dump class
- oo::meta::info class is type ?args?
- oo::meta::info class merge ?dict? ?dict? ?...?
- oo::meta::info class rebuild
- oo::meta::metadata class
- oo::define meta
- oo::class method meta
- oo::object method meta
- oo::object method meta cget ?field? ?...? field

## Description

The oo::meta package provides a data registry service for TclOO classes.

## Usage

    oo::class create animal {
      meta set biodata animal: 1
    }
    oo::class create mammal {
      superclass animal
      meta set biodata mammal: 1
    }
    oo::class create cat {
      superclass mammal
      meta set biodata diet: carnivore
    }
    cat create felix
    puts [felix meta dump biodata]
    > animal: 1 mammal: 1 diet: carnivore
    felix meta set biodata likes: {birds mice}
    puts [felix meta get biodata]
    > animal: 1 mammal: 1 diet: carnivore likes: {bird mice}
    # Modify a class
    mammal meta set biodata metabolism: warm-blooded
    puts [felix meta get biodata]
    > animal: 1 mammal: 1 metabolism: warm-blooded diet: carnivore likes: {birds mice}
    # Overwrite class info
    felix meta set biodata mammal: yes
    puts [felix meta get biodata]
    > animal: 1 mammal: yes metabolism: warm-blooded diet: carnivore likes: {birds mice}

## Concept

The concept behind oo::meta is that each class contributes a snippet of local data. When oo::meta::metadata is called, the system walks through the linear ancestry produced by oo::meta::ancestors, and recursively combines all of that local data for all of a class' ancestors into a single dict. Instances of oo::object can also combine class data with a local dict stored in the meta variable.

## COMMANDS

oo::meta::info

  oo::meta::info is intended to work on the metadata of a class in a manner similar to if the aggregate pieces where assembled into a single dict. The system mimics all of the standard dict commands, and addes the following:

oo::meta::info branchget ?key? ?...?

  Returns a dict representation of the element at args, but with any trailing : removed from field names.

      ::oo::meta::info $myclass set option color {default: green widget: colorselect}
      puts [::oo::meta::info $myclass get option color]
      > {default: green widget: color}
      puts [::oo::meta::info $myclass branchget option color]
      > {default green widget color}

oo::meta::info branchset ?key...? key value

  Merges dict with any other information contaned at node ?key...?, and adding a trailing : to all field names.

      ::oo::meta::info $myclass branchset option color {default green widget colorselect}
      puts [::oo::meta::info $myclass get option color]
      > {default: green widget: color}

oo::meta::info dump class

  Returns the complete snapshot of a class metadata, as producted by oo::meta::metadata

oo::meta::info class is type ?args?

  Returns a boolean true or false if the element ?args? would match string is type value

      ::oo::meta::info $myclass set constant mammal 1
      puts [::oo::meta::info $myclass is true constant mammal]
      > 1

oo::meta::info class merge ?dict? ?dict? ?...?

  Combines all of the arguments into a single dict, which is then stored as the new local representation for this class.

oo::meta::info class rebuild

  Forces the meta system to destroy any cached representation of a class' metadata before the next access to oo::meta::metadata

oo::meta::metadata class

  Returns an aggregate picture of the metadata for class, combining its local data with the local data from its ancestors.

oo::define meta

  The package injects a command oo::define::meta which works to provide a class in the process of definition access to oo::meta::info, but without having to look the name up.

      oo::define myclass {
        meta set foo bar: baz
      }

oo::class method meta

  The package injects a new method meta into oo::class which works to provide a class instance access to oo::meta::info.

oo::object method meta

  The package injects a new method meta into oo::object. oo::object combines the data for its class (as provided by oo::meta::metadata), with a local variable meta to produce a local picture of metadata. This method provides the following additional commands:

oo::object method meta cget ?field? ?...? field

  Attempts to locate a singlar leaf, and return its value. For single option lookups, this is faster than my meta getnull ?field? ?...? field], because it performs a search instead directly instead of producing the recursive merge product between the class metadata, the local meta variable, and THEN performing the search.

## Bugs, Ideas, Feedback

This document, and the package it describes, will undoubtedly contain bugs and other problems. Please report such in the category tcloo of the Tcllib Trackers. Please also report any ideas for enhancements you may have for either package and/or documentation.

When proposing code changes, please provide unified diffs, i.e the output of diff -u.

Note further that attachments are strongly preferred over inlined patches. Attachments can be made by going to the Edit form of the ticket immediately after its creation, and then using the left-most button in the secondary navigation bar.

## Keywords

TOOL, TclOO

## Category

TclOO

## Copyright

Copyright © 2015 Sean Woods <yoda@etoyoc.com>