How do I override a widget in order to provide some custom modifications to one of its property.
For example: Let's say I want to create my own Text widget which will convert whole text to uppercase. I'll do something like:
class MyOwnText extends Text {
MyOwnText(String data) : super(data.toUpperCase());
}
But with this approach, I can't use other properties of Text in my own widget, style, for example. For that, I'll have to add style property in my class constructor like this:
MyOwnText(String data, {TextStyle style}) : super(data.toUpperCase(), style: style);
But Text has got around 12-13 properties, and just to override one, I need to define all of those properties and then their assertion. I'm sure I may not be doing something right. Can anyone please help?
Note: Neither I want to use extension methods nor some client side code. MyOwnText should be a Text.
I get what you wanted to achieve, but I do not recommend to do this.
Why?? - Because most of the class has private variable and they have their separate getter and setter which are expose to the outer front of the class.
Again, If you wanted to for design and func. then you should not extend the widget. Instead you can directly use those in your build method
Why?? - You can't inherit more than one class(Mixin is other way around here)
So ultimately you need to assign properties directly or you could use spread operator
Related
I want to create some kind of 'wrapper' which is having getters for all my created custom-widgets in order to not need to remember them.
So I can than later use CustomWidgets().myCustomWidget to choose a specific one. Entering just CustomWidgets(). should display all available Widgets.
What I tried was setting it up like so:
class CustomWidgets {
CustomWidgets._();
Widget get solidButtonCustomGradient => SolidButton.customGradient(buttonLabel: buttonLabel, onPressed: onPressed, gradient: gradient)
}
But here I already have to apply all required parameter which I do not know in the wrapper class. Can't I just somehow call SolidButton in the wrapper and "redirects" to the constructor instead of creating here the object and returning the object by the wrapper?
I hope I formulated my desired behavior and maybe there already exist a way I do not know yet. Thank you :)
I am creating a custom widget, say "CustomWid" in UiBinder.
And in CustomWid.java file I am writing two constructors
one with zero args like
CustomWid(){....}
another with some args like
CustomWid(String a,String b){......}
So,Now I am using my custom widget in another .ui.xml file,in that .ui.xml file
it is working fine when we give
<my:CustomWid/> alone,
and also fine when we give like
<my:CustomWid a="srt1" b="str2"/> alone
But "MY PROBLEM" is whenever I am trying to give both the tags in the one .ui.xml as
<my:CustomWid/>
<my:CustomWid a="str1" b="str2"/>
Now it is throwing error when i am using both types of tags in a single .ui.xml
I mean How to use my custom widget tag like a prdefined tag?
I am using #uiConstructor, but it showing error
Please developers... I need answer as early as possible
UiBinder will only ever use a single constructor for a given widget: either its zero-arg constructor, or a #UiConstructor (I'm surprised that you say it works when using either one or the other call but not both: one should fail in every case, and one should succeed in every case; if you haven't annotated a constructor with #UiConstructor, then <my:CustomWid/> should always work and <my:CustomWid a="str1" b="str2"/> should always fail)
There are two solutions here:
use setters for the a and b attributes (void setA(String a) and void setB(String b))), and possibly check later (say, in onLoad or onAttach) that you have either none or both of A and B, but not one without the other (if that's your rule).
use #UiField(provided = true) when you need to use the other constructor (if you choose to have UiBinder use the zero-arg constructor –i.e. no #UiConstructor–, then that means you'll have to move the a="str1" b="str2" from the XML to the Java code: #UiField(provided = true) CustomWid myCustomWid = new CustomWid("str1", "str2")).
The first option has my preference.
It Will not show any errors...'
#UiConstructor
public Component(String displayText,String heading)
{
initWidget(uiBinder.createAndBindUi(this));
this.displayText.setText(displayText);
this.heading.setText(heading);
}`
now use another constructor with default parameters also it will work
public Component()
{
initWidget(uiBinder.createAndBindUi(this));
}
now if you add with xml parameters component and without parameters also works in the same page.
I've been reading up a bit about coffeescript's inheritance model and I have the feeling I'm on the fringes of an ideological debate which I really don't understand. So, I would be perfectly happy to find out that I'm just doing things in the wrong way.
Basically what I am doing is writing a set of widgets which, among other things, need to handle events on their DOM elements. I thought a good way to go about this would be to have a class method which would be called once, to delegate all the events which the widget might need. The base widget class might have some simple click handlers, while the subclass might add to that some mouseover handlers or extra click handlers.
However, it appears that I'm not supposed to try and do the equivalent of calling super() inside a static method. There is a workaround which exists, (this.__super__.constructor.METHODNAME() but I've seen a lot of suggestions that this isn't the best way to do what I'm trying to do. Has anyone got any insights on how I should structure this code? Keep using the workaround, or put all the delegation into a totally different place? I can't really just stick it in the prototype, since I won't necessarily have an instance to call the method on (or can I essentially still call a method on the prototype from a static context, like putting SwatchableWidget.prototype.delegateEvents() into an onload function or something?
Here's a bit of code to illustrate what I'm talking about:
class Widget
#testProp: "ThemeWidget"
#delegateEvents: ->
console.log "delegate some generic events"
class SwatchableWidget extends Widget
#testProp2 = "SwatchWidget"
#delegateEvents: ->
console.log "delegate some specific swatchable widget events"
this.__super__.constructor.delegateEvents()
Widget.delegateEvents()
SwatchableWidget.delegateEvents()
Thanks for any help.
I suggest replacing
this.__super__.constructor.delegateEvents()
with
Widget.delegateEvents()
trying to use super to call static methods is not required (and doesn't make much sense)
I don't understand why delegateEvents would be a class-level method, or why Widget.delegateEvents have to be called again from SwatchableWidget.delegateEvents. If it's just class initialization code, you should put it in the class body directly:
class Widget
console.log "delegate some generic events"
...
#testProp: "ThemeWidget"
class SwatchableWidget extends Widget
console.log "delegate some specific swatchable widget events"
...
#testProp2 = "SwatchWidget"
I take it you're waiting for a specific DOM state before running this initialization code? Maybe I could suggest another approach if you told me a little bit more about the preconditions for delegateEvents.
It sounds like you want a different type of inheritance model where each inherited function of a certain type ("parent calling") will walk the inheritance tree and call all its parents with the same name.
You could call any direct parent functions in each child manually as you've written. Then it will float up the inheritance chain anywhere you specify such a relationship.
I would bind the parents delegate call in the constructor to a current class function
delegateparents =>
#call any parent class methods
This may sound very weird, but let's start with an example:
<my:MagicWidget ui:field="someFieldName" fieldName="someFieldName"/>
It's pretty much asured that we'll always want to have the same value in ui:field and in fieldName. Clearly there is some duplucation in this code, I'd like to avoid it and make the fieldName optional.
So, this is what I have in the widget's code:
#UiConstructor
public MagicWidget(String fieldName) {
this.fieldName = fieldName;
}
But I'd like, if possible to allow this constructor to be optional, and provide an default constructor that would "by magic" find out it's ui:field value:
#UiConstructor
public MagicWidget() {
this.fieldName = /*some magic to get ui:field's value*/;
}
I was wondering if there is a way to get the value of "ui:field" inside my MagickWidget? (The widget extends Composite). I fear this might not be possible, because most of the time it's not so useful, but if anyone has an idea - feel free to share!
PS: I'm using GWT 2.1.0.RC1.
As you may know, the ui:field is there so you can interact with a UI Object in Java code after you've declared it with UiBinder. So, for example, if you add a MagicWidget in a UiBinder template, you can write
#UiField MagicWidget someWidget
in order to be able to interact with it programatically. Having your magic widget aware of the name of the reference that is pointing to it might not be all that helpful (or possible), as you can pass the reference to that specific MagicWidget back and forth between different parts of your application. A single MagicWidget could easily have several references with different names pointing at is simultaneously. That's why it's difficult to pick it out "by magic" at runtime. I realize this isn't much of an issue if you only want this value when the object is constructed, but keep in mind that you're not required to include a ui:field when you add a widget using UiBinder.
Why is it important that the Widget know its field name? Knowing that might make it easier to provide suggestions about other ways to accomplish what you are looking to do.
i'm trying to dynamically add the class attribute to the body tag, and i came across this class. but i can't seem to understand how to use this class. i have something like this in my page class (or panel class, as i tried with that too):
add(new BodyTagAttributeModifier("class", "homepage", this));
this doesn't even compile, saying there's something wrong with the 2nd parameter. but i think String is automatically considered a Model in wicket, like the Label class. am i missing something here?
What if you just add an wicket:id to the body attribute and use the AttributeAppender class? Or, if the body attribute already has an id, can't you just use this class?
http://wicket.sourceforge.net/apidocs/wicket/behavior/AttributeAppender.html
Some Wicket Components have this String-to-model-shortcut (like Label), but it's not a general feature. You have to convert your String into a Model manually:
add(new BodyTagAttributeModifier("class", Model.of("homepage"), this));