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/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
#include "nsIArray.idl"
/**
* Helper interface for allowing scripts to treat nsIArray instances as if
* they were nsISupportsArray instances while iterating.
*
* nsISupportsArray is convenient to iterate over in JavaScript:
*
* for (let i = 0; i < array.Count(); ++i) {
* let elem = array.GetElementAt(i);
* ...
* }
*
* but doing the same with nsIArray is somewhat less convenient, since
* queryElementAt is not nearly so nice to use from JavaScript. So we provide
* this extension interface so interfaces that currently return
* nsISupportsArray can start returning nsIArrayExtensions and all JavaScript
* should Just Work. Eventually we'll roll this interface into nsIArray
* itself, possibly getting rid of the Count() method, as it duplicates
* nsIArray functionality.
*/
[scriptable, builtinclass, uuid(261d442e-050c-453d-8aaa-b3f23bcc528b)]
interface nsIArrayExtensions : nsIArray
{
/**
* Count()
*
* Retrieves the length of the array. This is an alias for the
* |nsIArray.length| attribute.
*/
uint32_t Count();
/**
* GetElementAt()
*
* Retrieve a specific element of the array. null is a valid result for
* this method.
*
* Note: If the index is out of bounds null will be returned.
* This differs from the behavior of nsIArray.queryElementAt() which
* will throw if an invalid index is specified.
*
* @param index position of element
*/
nsISupports GetElementAt(in uint32_t index);
};
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