warn-assignment-in-condition.qdoc

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// Copyright (C) 2025 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GFDL-1.3-no-invariants-only
 
/*!
\page qmllint-warnings-and-errors-assignment-in-condition.html
\ingroup qmllint-warnings-and-errors
 
\title Warn about using assignment in conditions
\brief [assignment-in-condition] An assignment statement is used inside a condition
 
\qmllintwarningcategory assignment-in-condition
 
\section1 Warn about using assignment in conditions
 
\section2 What happened?
You used an assignment inside an \c{if-condition}.
 
\section2 Why is this bad?
This is often a mistake, and a comparison should have been used. If it was intentional, it is still
often considered confusing.
 
\section2 Example
\qml
import QtQuick
 
Item {
    id: root
    Component.onCompleted: {
       // mistake: should have been a comparison
       if (width = height)
           console.log("A square")
       let mypoint = Qt.point(1,2)
       let hit = false
       // intentional, but possibly misleading
       if (hit = root.contains(myPoint))
           console.log("hit")
       root.enabled = hit
    }
}
\endqml
 
To fix this warning, change the assignment to a comparison if it was a mistake. Otherwise, wrap the
assignment into parentheses to indicate that it was done intentionally.
 
\qml
import QtQuick
 
Item {
    id: root
    Component.onCompleted: {
       // fixed
       if (width === height)
           console.log("A square")
       let mypoint = Qt.point(1,2)
       let hit = false
       // intentional
       if ((hit = root.contains(point)))
           console.log("hit")
       root.enabled = hit
    }
}
\endqml
*/