Communication between ViewModel and Composer"
From Documentation
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| − | + | In order to understand the following paragraphs, you had better understand [[ZK Developer's Reference/MVVM/ViewModel/Commands#Global_Command | concept of global command]] and [[ZK Developer's Reference/MVVM/Data Binding/Global Command Binding| how to bind an event to it]]. | |
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| + | The [[ZK Developer's Reference/MVVM/Data Binding/Global Command Binding#Usage | global command binding usage section]] demonstrates how to communicate between multiple ViewModels. We can also use the same mechanism to perform communication between a composer and a ViewModel, but usage is a little different. | ||
=Posting a Command from a Composer to a ViewModel = | =Posting a Command from a Composer to a ViewModel = | ||
| − | + | We have already known that global command is triggered by [[ZK Developer's Reference/MVVM/Data Binding/Binder| binder sending events into event queue]]. Hence ViewModels can communicate each other by their own binders. But a composer doesn't have a binder to send a global command for it. Therefore, we provide a utility class, '''<javadoc> org.zkoss.bind.BindUtils </javadoc>''', that can do this job. You can use it in a composer. | |
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| − | + | For example, after adding a product, you want to tell <tt> ShoppingCartViewModel </tt> to refresh shopping cart's items. | |
| − | + | ''' Send a global command in a composer (Sender)''' | |
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| − | + | <source lang="java" high="8"> | |
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| − | + | public class MyComposer extends SelectorComposer{ | |
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| + | @Listen("onAddProductOrder=#PrdoDiv #prodGrid row productOrder") | ||
| + | public void addProduct(Event fe) { | ||
| − | + | //business logic of adding a product | |
| − | + | BindUtils.postGlobalCommand(null, null, "updateShoppingCart", null); | |
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} | } | ||
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} | } | ||
</source> | </source> | ||
| − | + | * we use <tt> BindUtils.postGlobalCommand(String queueName, String queueScope, String cmdName, Map<java.lang.String,java.lang.Object> args) </tt> to post a command. We leave first two arguments as "null" to use default queue name and default scope ('''desktop'''). The third arguments is '''global command's name'''. You can send extra data with a Map by the fourth argument. (line 19) | |
| − | + | * The specified global command is then executed by all ViewModel's binders that have subscribed to the event queue in the same (desktop) scope. | |
| − | <source lang="java"> | + | |
| + | In the ShoppingCartViewModel, we should declare a global command method named "updateShoppingCart" to receive this command request and refresh cart items. The code snippet below shows this. | ||
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| + | '''Global command in a ViewModel (Receiver)''' | ||
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| + | <source lang="java" high="5,7"> | ||
public class ShoppingCartViewModel { | public class ShoppingCartViewModel { | ||
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@NotifyChange("cartItems") | @NotifyChange("cartItems") | ||
public void updateShoppingCart() { | public void updateShoppingCart() { | ||
| − | // | + | //update shopping cart |
} | } | ||
} | } | ||
</source> | </source> | ||
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Revision as of 07:51, 17 May 2012
This page is under construction, so we cannot guarantee the accuracy of the content!
In order to understand the following paragraphs, you had better understand concept of global command and how to bind an event to it.
The global command binding usage section demonstrates how to communicate between multiple ViewModels. We can also use the same mechanism to perform communication between a composer and a ViewModel, but usage is a little different.
Posting a Command from a Composer to a ViewModel
We have already known that global command is triggered by binder sending events into event queue. Hence ViewModels can communicate each other by their own binders. But a composer doesn't have a binder to send a global command for it. Therefore, we provide a utility class, BindUtils, that can do this job. You can use it in a composer.
For example, after adding a product, you want to tell ShoppingCartViewModel to refresh shopping cart's items.
Send a global command in a composer (Sender)
public class MyComposer extends SelectorComposer{
@Listen("onAddProductOrder=#PrdoDiv #prodGrid row productOrder")
public void addProduct(Event fe) {
//business logic of adding a product
BindUtils.postGlobalCommand(null, null, "updateShoppingCart", null);
}
}
- we use BindUtils.postGlobalCommand(String queueName, String queueScope, String cmdName, Map<java.lang.String,java.lang.Object> args) to post a command. We leave first two arguments as "null" to use default queue name and default scope (desktop). The third arguments is global command's name. You can send extra data with a Map by the fourth argument. (line 19)
- The specified global command is then executed by all ViewModel's binders that have subscribed to the event queue in the same (desktop) scope.
In the ShoppingCartViewModel, we should declare a global command method named "updateShoppingCart" to receive this command request and refresh cart items. The code snippet below shows this.
Global command in a ViewModel (Receiver)
public class ShoppingCartViewModel {
...
@GlobalCommand
@NotifyChange("cartItems")
public void updateShoppingCart() {
//update shopping cart
}
}
Posting a Command from a ViewModel to a Composer
Version History
| Version | Date | Content |
|---|---|---|
| 6.0.0 | May 2012 | Supplement to advanced topic. |