A problem transfering a parameter through a loader.

Alicemirror

Hi to all,

i am experiencing a strange problem with the loader mechanism.

The calling document instantiates the loader and pass to it a series of properties defined in the loader QML document. Here is a small example showing the mechanism:

MyApp.qml includes

@
Item {
id: appItem

// Properties to customize the loader document
property string theme: "xxx"
property string title: "The object title"

[...]

// Loader component instance
MyLoader {
id: loaderInstance

// Properties assignement
theme: appItem.theme
title: appaItem.title

[... other stuff ...]

// Absolute document name
obj: "DocToLoad"

}
@

Thus MyLoader.qml is defined as follows:

@
Item {
id: docLoader

property string theme: ""
property string title: ""
property string obj: ""

Loader {
id: loadObj

[... various stuff ...]
function getTheme() { return docLoader.theme; }
function getTitle() { return docLoader.title; }

source: docLoader.obj + ".qml"

[... code managing component signals ...]
}
@

The problem happens in the loaded object. Take in account that despite this example there is a lot of other parameters passed from the calling application to the destination component throught the loader and all the other works.
The DocToLoad.qml is defined as follows:

@
Item {
id: loadableObject

[... the loadable object code ...]

text {
id: myText

[ ...]

text: loadObj.getTitle();

}

Image {
id: myImage

source: "images/'+ loadObj.getTheme() + "/myPicture.png"

[....]

}
@

All the parameters passed transparently throught the loader to the loadable object from the calling application works fine including file names.
The console error that I get is something like
@
Could not find the image "images//myPicture.png"
@
just as the theme property is not passed at all. Instead the theme property works if in MyApp.qml I assign explicitly the value to the loadObj.theme property, e.g.

@
// Loader component instance
MyLoader {
id: loaderInstance

// Properties assignement
theme: "xxx"
title: appaItem.title

[... other stuff ...]

// Absolute document name
obj: "DocToLoad"

}
@

In any other way this particular custom property don't work at all. Using loaders intensively this means to replicate the string instead of using a property.

Any help is appreciated.

Cheers :)

thisisbhaskar

I don't know if I understood your question correctly.. but did you try aliases rather than normal properties.

@
// Properties to customize the loader document
property string theme: "xxx"
property string title: "The object title"
@

to

@
// Properties to customize the loader document
property alias theme: loaderInstance.them
property alias title: loaderInstance.title

Component.onCompleted: {
// assign the values here...
}
@

Alicemirror

Thank you very much Vijay, it is a good test.

What it is needed is to define the (theme) property once and apply it in many different loader instances. The alias assignement do the opposite as I have interpreted: you assign a alias for every instance, that is what I avoid. It is possible that I have misunderstood this method ?

The real solution I missed probably is Component.onCompleted { ... } This can be the reason of the parameter is not passed correctly.