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Module: hook | Twisted-0.17.4/twisted/python/hook.py
--- | ---

I define support for hookable instance methods.

These are methods which you can register pre-call and post-call external functions to augment their functionality. People familiar with more esoteric languages may think of these as \"method combinations\".

This could be used to add optional preconditions, user-extensible callbacks (a-la emacs) or a thread-safety mechanism.

### The four exported calls are:

- addPre

- addPost

- removePre

- removePost

All have the signature (class, methodName, callable), and the callable they take must always have the signature (instance, args, *kw) unless the particular signature of the method they hook is known.

Hooks should typically not throw exceptions, however, no effort will be made by this module to prevent them from doing so. Pre-hooks will always be called, but post-hooks will only be called if the pre-hooks do not raise any exceptions (they will still be called if the main method raises an exception). The return values and exception status of the main method will be propogated (assuming none of the hooks raise an exception). Hooks will be executed in the order in which they are added.

Imported modules |
--- | ---
import reflect import string
Functions |

ORIG POST PRE _XXX _addHook _dehook | _enhook _removeHook addPost addPre removePost removePre

| ORIG

    ORIG ( k,  n )

(private) munging to turn a method name into an `original' identifier

| POST

    POST ( k,  n )

(private) munging to turn a method name into a post-hook-method-name

| PRE

    PRE ( k,  n )

(private) munging to turn a method name into a pre-hook-method-name

| _XXX

    _XXX (
            k,
            n,
            s,
            )

string manipulation garbage

| _addHook

    _addHook (
            klass,
            name,
            phase,
            func,
            )

(private) adds a hook to a method on a class

| _dehook

    _dehook ( klass,  name )

(private) causes a certain method name no longer to be hooked on a class

Exceptions |
--- | ---
HookError( "Cannot unhook!" )

| _enhook

    _enhook ( klass,  name )

(private) causes a certain method name to be hooked on a class

| _removeHook

    _removeHook (
            klass,
            name,
            phase,
            func,
            )

(private) removes a hook from a method on a class

Exceptions |
--- | ---
HookError( "no hooks present!" ) HookError("hook %s not found in removal list for %s" %( name, klass ) )

| addPost

    addPost (
            klass,
            name,
            func,
            )

### hook.addPost(klass, name, func) -> None

Add a function to be called before the method klass.name is invoked.

| addPre

    addPre (
            klass,
            name,
            func,
            )

### hook.addPre(klass, name, func) -> None

Add a function to be called before the method klass.name is invoked.

| removePost

    removePost (
            klass,
            name,
            func,
            )

### hook.removePre(klass, name, func) -> None

Remove a function (previously registered with addPost) so that it is no longer executed after klass.name.

| removePre

    removePre (
            klass,
            name,
            func,
            )

### hook.removePre(klass, name, func) -> None

Remove a function (previously registered with addPre) so that it is no longer executed before klass.name.

Classes |

HookError | An error which will fire when an invariant is violated.

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This document was automatically generated on Sat Apr 20 01:31:23 2002 by HappyDoc version 2.0