alias-cycle.qdoc

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// Copyright (C) 2023 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GFDL-1.3-no-invariants-only
 
/*!
\page qmllint-warnings-and-errors-alias-cycle.html
\ingroup qmllint-warnings-and-errors
 
\title Alias cycle
\brief [alias-cycle] Alias property is part of an alias cycle.
 
\qmllintwarningcategory alias-cycle
 
\section1 Alias property is part of an alias cycle
 
\section2 What happened?
A \l{QML Object Attributes#property-aliases}{property alias} resolves to itself or to another
alias resolving to itself.
 
Usually, \l{QML Object Attributes#property-aliases}{a property alias} should reference another
property either directly, or indirectly by passing through another alias property.
 
If a property alias directly or indirectly references itself, then it forms an alias cycle.
The warning indicates that the current alias property is inside or references
an alias cycle, see \l{#example}{Example}.
 
\section2 Why is this bad?
Instances of components with alias cycles will not be created at runtime: they will be null instead.
 
\section2 Example
\qml
import QtQuick
 
Item {
    id: someId
    property alias myself: someId.myself // not ok: referring to itself
 
    property alias cycle: someId.cycle2 // not ok: indirectly referring to itself
    property alias cycle2: someId.cycle
 
    property alias indirect: someId.cycle // not ok: referring to alias indirectly referring to itself
}
\endqml
To fix this warning, break up the alias cycles:
\qml
import QtQuick
 
Item {
    id: someId
    Item {
        id: anotherId
        property string myself
        property int cycle
    }
    property alias myself: anotherId.myself // ok: referring to a property
 
    property alias cycle: someId.cycle2 // ok: does not refer to itself anymore
    property alias cycle2: anotherId.cycle // ok: not a cycle anymore
 
    property alias indirect: someId.cycle // ok: cycle does not form an alias cycle anymore
}
\endqml
*/