---
name: "oometa"
section: "3tcl"
platform: "linux"
package: "tcllib"
version: "2.0+dfsg-4"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/oometa"
---

# oometa(3tcl)

oo::meta A data registry for classess

```

```

## 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* \[http://core.tcl.tk/tcllib/reportlist\]. 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 (c) 2015 Sean Woods <yoda@etoyoc.com>
```