"Unknown component. (M300)" for custom QML class

[Phrogz]

Summary: Referencing my custom QML widget that is in a different directory results in Qt Creator highlighting it as an error, flagged with the message "Unknown component. (M300)". However, the QML resolves correctly at runtime without error. How can I fix Qt Creator to not act like a dunce?

I have this physical directory structure:

MyProject/
    main.qml
    CommonWidget.qml
    screens/
        Screen1.qml

My .qrc looks like this:

<RCC>
    <qresource prefix="/">
        <file>main.qml</file>
        <file>CommonWidget.qml</file>
        <file alias="Screen1.qml">screens/Screen1.qml</file>
    </qresource>
</RCC>

Inside of Screen1.qml the code is roughly:

import QtQuick 2.6

Item {
    CommonWidget { /* ...content here... */ }              // Error: Unknown component. (M300)
    // other stuff
}

Per this StackOverflow answer I tried adding import "../screens" to my QML, but that did not change Qt Creator's behavior.

[Diracsbracket]

@Phrogz
Why add import "../screens" in Screen1.qml, since CommonWidget.qml is defined in the parent directory of the screens directory?

To use CommonWidget in Screen1.qml, you can use :

import ".."

Otherwise, if all is correct, you may need to re-run qmake first to get QtCreator to recognize the new component after adding the file to the project...

[Phrogz]

The problem goes away and shows up again as I add new QML. The import statement is unnecessary. The (surely overkill) steps I've used to fix it:

1. Quit Qt Creator
2. Delete all output directories from disk
3. Delete the .pro.user file.
4. Launch Qt Creator and re-open the project (re-setting up the .pro.user in the process).

When I do those steps, this problem always goes away.

[shaan7]

Did you try Tools > QML/JS > Reset Code Model? Usually works for me.

[paghsa]

@shaan7
thanks this was really helpful

[Tom_Kruise]

@shaan7 This 2 mouse click solution worked for me, solving the head scratching problem of Qt Creator "unknown component (M300)" errors for ListModel and ListElement. Thanks.

[equati0n]

@shaan7 Worked for me too. I was also having the problem of "unknown component (M300)" error for ListModel and ListElement. Thanks.

[JsonYang]

@shaan7 thanks!perfect solution!

[e.sinoheh]

@shaan7 Works like magic