I'm trying to create an instance of a QtMobility MapPolyline and several of Coordinate in QML programmaticaly from a Javascript function.
As far as I can see the only way to create new instance from Javascript functions is to use Qt.createComponent and Qt.createQmlObject. However, I can't find a way to call createComponent that will work (I always get a file doesnt exist error). And I'd like to avoid Qt.createQmlObject since it seems like a really bad practice.
Is there any clean way to achieve this?
Component {
id: polyGenerator
MapPolyline {}
}
function addPoly() {
//This next line works, but crashes when trying to add positions
//createPoly(polyGenerator);
var component = Qt.createComponent("Rectangle");
console.log(component.status + " " + Component.Null);
if (component.status == Component.Ready) {
createPoly(component);
} else if (component.status == Component.Error) {
console.log("Error: " + component.errorString());
} else {
component.statusChanged.connect(function () {
if (component.status == Component.Error) {
console.log("Error: " + component.errorString());
return;
}
createPoly(component);
});
}
}
function createPoly(component) {
var poly = component.createObject(map);
poly.border.color = "red";
poly.border.width = 4;
// I get a crash here, my guess is that I need proper Coordinate objects
poly.addCoordinate({latitude: -34.60553, longitude: -58.38088});
poly.addCoordinate({latitude: -34.60720, longitude: -58.38081});
poly.addCoordinate({latitude: 34.60720, longitude: -58.38081});
poly.addCoordinate({latitude: -34.60597, longitude: -58.37930});
map.addMapObject(poly);
}
Qt.createComponent needs a URL to load a file from. That's why it complains about a missing file; you're trying to load a file called "Rectangle".
If you just want to create objects dynamically create your component declarative.
Component {
id: component
Rectangle {
}
}
That way the createPoly function should work fine.
Related
I am trying to dynamically translate some text to be displayed when a user clicks on the translate button, but I can't get it to save my values outside of the Promise. I haven't worked much with Promises and every example only shows console.log, rather than saving values outside of the Promise. I don't really understand how they work. Here is (most of) the code I am trying to fix:
constructor(props) {
super(props);
this.state = {
dynamicTranslate: this.props.dynamicTranslate,
};
}
// I've tried this method as both sync and async (with await) but neither work
googleTranslate = (key) => {
const translator = TranslatorFactory.createTranslator();
// translate returns a Promise
return translator.translate(key, i18n.locale)
.then((response) => {return response});
}
renderText() {
// getting some values....
// this loops through all the feedback information
for (var i = 0; i < components_feedback.length; i++) {
let label = (some string);
let value = (some string);
// to do: call google translate call here if Boolean(this.state.dynamicTranslate)
if (Boolean(this.state.dynamicTranslate)) {
// I am ultimately trying to save the translation string from googleTranslate()
// in label/value so I can push it into feedbacks
label = this.googleTranslate(label);
value = this.googleTranslate(value);
}
feedbacks.push({label: label, value: value, type: comp.type})
}
return (
// some stuff
feedbacks.map((feedback, index)) => {
// some stuff
<Text>{feedback.label}</Text>
<Text>{feedback.value}</Text>
// some other stuff
});
);
}
render() {
return (
<View>{this.renderText()}</View>
);
}
One of the issues I'm running into is that label/value is a Promise if translation is on. If I try to make renderText() an async method, it is also turned into a Promise which render() can't handle. No idea where to go from here.
Solved this issue. Solution is to put the loop in an async function that (ideally) gets called on construction. This loop was edited to await the returns and push to local arrays of labels and values then saves those in state. You can compare the length of those arrays to the expected length (compare length of last array being used to be positive that it has finished) and that is how you can know if the Promises have returned. Paraphrased code:
constructor(props) {
this.state = {
translatedLabels = []
translatedValues = []
}
this.asyncFunction()
}
asyncFunction = () => {
labels = []
for loop
label = await promise
labels.push(label)
//same for values
end for
this.setState({translatedLabels: labels})
}
//later
renderText() {
if (this.state.translatedLabels.length === whatever) {
// do your stuff as you know the async function has finished
}
}
render() {
return (
{this.renderText()}
);
}
I'm trying to build a dynamic Vue system, where I want to insert custom components knowing only their name. Inspiration from here took me to do:
export default {
name: 'MySite',
mixins: [MyMixin],
components: {MyComponent1, MyComponent2},
...
}
...
mounted() {
var ComponentClass = Vue.extend(MyComponent1)
var instance = new ComponentClass()
instance.$mount() // pass nothing
this.$refs.container.appendChild(instance.$el)
}
Now I want to do the same thing, but knowing only the component name 'MyComponent1' as String. What is the way to do it ? I guess it's more related to pure JavaScript than Vue, but I can't figure out how to do it.
you are right is a simple js.
look at the example below, most importend thing is eval()
class Polygon {
constructor(height, width) {
this.height = height;
this.width = width;
}
get getHeight() {
return this.height
}
}
// js string code
var code = "new Polygon(15, 200)";
// convert it to code;
var cls = eval(code);
console.log(cls.getHeight)
I found that using
this.$options.__proto__.components['MyComponent1']
works and do what I want. Is it the cleanest solution ?
I'm learning Vue and have been struggling to get the data from a computed property. I am retrieving comments from the store and them processing through a function called chunkify() however I'm getting the following error.
Despite the comments being computed correctly.
What am I doing wrong here? Any help would be greatly appreciated.
Home.vue
export default {
name: 'Home',
computed: {
comments() {
return this.$store.state.comments
},
},
methods: {
init() {
const comments = this.chunkify(this.comments, 3);
comments[0] = this.chunkify(comments[0], 3);
comments[1] = this.chunkify(comments[1], 3);
comments[2] = this.chunkify(comments[2], 3);
console.log(comments)
},
chunkify(a, n) {
if (n < 2)
return [a];
const len = a.length;
const out = [];
let i = 0;
let size;
if (len % n === 0) {
size = Math.floor(len / n);
while (i < len) {
out.push(a.slice(i, i += size));
}
} else {
while (i < len) {
size = Math.ceil((len - i) / n--);
out.push(a.slice(i, i += size));
}
}
return out;
},
},
mounted() {
this.init()
}
}
Like I wrote in the comments, the OPs problem is that he's accessing a store property that is not available (probably waiting on an AJAX request to come in) when the component is mounted.
Instead of eagerly assuming the data is present when the component is mounted, I suggested that the store property be watched and this.init() called when the propery is loaded.
However, I think this may not be the right approach, since the watch method will be called every time the property changes, which is not semantic for the case of doing prep work on data. I can suggest two solutions that I think are more elegant.
1. Trigger an event when the data is loaded
It's easy to set up a global messaging bus in Vue (see, for example, this post).
Assuming that the property is being loaded in a Vuex action,the flow would be similar to:
{
...
actions: {
async comments() {
try {
await loadComments()
EventBus.trigger("comments:load:success")
} catch (e) {
EventBus.trigger("comments:load:error", e)
}
}
}
...
}
You can gripe a bit about reactivity and events going agains the reactive philosophy. But this may be an example of a case where events are just more semantic.
2. The reactive approach
I try to keep computation outside of my views. Instead of defining chunkify inside your component, you can instead tie that in to your store.
So, say that I have a JavaScrip module called store that exports the Vuex store. I would define chunkify as a named function in that module
function chunkify (a, n) {
...
}
(This can be defined at the bottom of the JS module, for readability, thanks to function hoisting.)
Then, in your store definition,
const store = new Vuex.Store({
state: { ... },
...
getters: {
chunkedComments (state) {
return function (chunks) {
if (state.comments)
return chunkify(state.comments, chunks);
return state.comments
}
}
}
...
})
In your component, the computed prop would now be
computed: {
comments() {
return this.$store.getters.chunkedComments(3);
},
}
Then the update cascase will flow from the getter, which will update when comments are retrieved, which will update the component's computed prop, which will update the ui.
Use getters, merge chuckify and init function inside the getter.And for computed comment function will return this.$store.getters.YOURFUNC (merge of chuckify and init function). do not add anything inside mounted.
I currently have an issue with a file read in a Windows 8/WinRT application. I have a simple navigation style app, several pages have access to the same data and I have a data.js file that defines a namespace (Data) with a number of members. One part of the application saves items to a txt file stored in the applications local data folder. But on some of the other pages I need to read this in or check for the existence of an item within the list of previously saved items. To do this I added another method into the data.js file. The trouble is, when I call this method to check for the existence of an item, it doesn't return the value straight away due to the async nature, but the rest of code in the page specific js file still seems to execute before it jumps back into the parsing. This means that the logic to check for an item doesn't seem to work. I have a feeling it's down to my use of either .done or .then but my code is as follows:
DATA.JS
var doesItemExist= function(item_id){
var appFolder = Windows.Storage.ApplicationData.current.localFolder;
//note I've tried this with and without the first "return" statement
return appFolder.getFileAsync(dataFile).then(function (file) {
Windows.Storage.FileIO.readTextAsync(file).done(function (text) {
try {
var json = JSON.parse(text);
if (json) {
for (var i = 0; i < json.items.length; i++) {
var temp_item = json.items[i];
if (temp_item.id === item_id) {
return true;
break;
}
}
} else {
return false;
}
} catch (e) {
return false;
console.log(e);
}
}, function (e) { return false;console.log(e); });
}, function (e) { // error handling
return false;
console.log(e);
});
}
WinJS.Namespace.define("Data", {
doesItemExist: doesItemExist
}); //all of the above is wrapped in a self executing function
Then on Page.js I have the following:
var add = document.getElementById('add');
if (Data.doesItemExist(selected_item.id)) {
add.style.display = 'block';
} else {
add.style.display = 'none';
}
All the variables here are assigned and debugging doesn't produce any errors, control just appears to go back to the if/else statement after it hits the getFileAsync but before it even goes through the for loop. But subsequently it does go in to the for loop but after the if statement has finished. I'm guessing this is down to the async nature of it all, but I'm not sure how to get around it. Any ideas?
thanks
A Promise should work here.
I created a new Navigation app, and added a Data.js file containing the following code:
(function () {
var appData = Windows.Storage.ApplicationData;
function doesItemExist(item_id) {
return new WinJS.Promise(
function (completed, error, progress) {
var exists = false;
appData.current.localFolder.createFileAsync("data.txt", Windows.Storage.CreationCollisionOption.openIfExists).then(
function (file) {
Windows.Storage.FileIO.readTextAsync(file).then(
function (fileContents) {
if (fileContents) {
if (fileContents = "foo!") {
completed(true);
}
else {
completed(false);
}
}
else {
completed(false);
}
}
);
},
function (e) {
error(e);
}
);
}
);
}
WinJS.Namespace.define("Data", {
doesItemExist: doesItemExist
});
})();
Note that I've simplified the code for retrieving and parsing the file, since that's not really relevant to the problem. The important part is that once you've determined whether the item exists, you call completed(exists) which triggers the .then or .done of the Promise you're returning. Note that you'd call error(e) if an exception occurs, as I'm doing if there's an exception from the call to createFileAsync (I use this call rather than getFileAsync when I want to be able to either create a file if it does not exist, or return the existing file if it does, using the openIfExists option).
Then, in Home.js, I added the following code to the ready handler:
var itemExists;
var itemExistsPromise = Data.doesItemExist(42);
itemExistsPromise = itemExistsPromise.then(function (exists) {
itemExists = exists;
var content = document.getElementById("content");
content.innerText = "ItemExists is " + itemExists;
});
itemExistsPromise.done(function () {
var a = 42;
});
var b = 0;
The code above sets the variable itemExistsPromise to the returned promise from the function in Data.js, and then uses an anonymous function in the .then function of the Promise to set the variable itemExists to the Boolean value returned from the doesItemExist Promise, and grabs the <p> tag from Home.html (I added an id so I could get to it from code) and sets its text to indicate whether the item exists or not). Because I'm calling .then rather than .done, the call returns another promise, which is passed into the itemExistsPromise variable.
Next, I call itemExistsPromise.done to do any work that has to wait until after the work performed in the .then above it.
If you set a breakpoint on the lines "var a = 42" and "var b = 0" (only included for the purpose of setting breakpoints) as well as on the line "itemExists = exists", you should find that this gives you the control you need over when the various parts are executed.
Hope that helps!
In my ExtJS 4.0.7 app I have some 3rd party javascripts that I need to dynamically load to render certain panel contents (some fancy charting/visualization widgets).
I run in to the age-old problem that the script doesn't finish loading before I try to use it. I thought ExtJS might have an elegant solution for this (much like the class loader: Ext.Loader).
I've looked at both Ext.Loader and Ext.ComponentLoader, but neither seem to provide what I'm looking for. Do I have to just "roll my own" and setup a timer to wait for a marker variable to exist?
Here's an example of how it's done in ExtJS 4.1.x:
Ext.Loader.loadScript({
url: '...', // URL of script
scope: this, // scope of callbacks
onLoad: function() { // callback fn when script is loaded
// ...
},
onError: function() { // callback fn if load fails
// ...
}
});
I've looked at both Ext.Loader and Ext.ComponentLoader, but neither
seem to provide what I'm looking for
Really looks like it's true. The only thing that can help you here, I think, is Loader's injectScriptElement method (which, however, is private):
var onError = function() {
// run this code on error
};
var onLoad = function() {
// run this code when script is loaded
};
Ext.Loader.injectScriptElement('/path/to/file.js', onLoad, onError);
Seems like this method would do what you want (here is example). But the only problem is that , ... you know, the method is marked as private.
This is exactly what newest Ext.Loader.loadScript from Ext.4-1 can be used for.
See http://docs.sencha.com/ext-js/4-1/#!/api/Ext.Loader-method-loadScript
For all you googlers out there, I ended up rolling my own by borrowing some Ext code:
var injectScriptElement = function(id, url, onLoad, onError, scope) {
var script = document.createElement('script'),
documentHead = typeof document !== 'undefined' && (document.head || document.getElementsByTagName('head')[0]),
cleanupScriptElement = function(script) {
script.id = id;
script.onload = null;
script.onreadystatechange = null;
script.onerror = null;
return this;
},
onLoadFn = function() {
cleanupScriptElement(script);
onLoad.call(scope);
},
onErrorFn = function() {
cleanupScriptElement(script);
onError.call(scope);
};
// if the script is already loaded, don't load it again
if (document.getElementById(id) !== null) {
onLoadFn();
return;
}
script.type = 'text/javascript';
script.src = url;
script.onload = onLoadFn;
script.onerror = onErrorFn;
script.onreadystatechange = function() {
if (this.readyState === 'loaded' || this.readyState === 'complete') {
onLoadFn();
}
};
documentHead.appendChild(script);
return script;
}
var error = function() {
console.log('error occurred');
}
var init = function() {
console.log('should not get run till the script is fully loaded');
}
injectScriptElement('myScriptElem', 'http://www.example.com/script.js', init, error, this);
From looking at the source it seems to me that you could do it in a bit of a hackish way. Try using Ext.Loader.setPath() to map a bogus namespace to your third party javascript files, and then use Ext.Loader.require() to try to load them. It doesn't look like ExtJS actually checks if required class is defined in the file included.