Building Applications with Force.com and VisualForce (DEV401) （二五）：Visualforce Controller

Dev401-026:Visualforce Pages: Visualforce Controller

 

Module Objectives
1.Identify the functionality that comes with each standard controller
2.Realize when you would need to move to Apex for creating custom controllers or extensions.
3.Compare and contrast controllers and extensions.

Module Agenda
1.Controller Overview
2.Standard Controllers
3.Custom Controllers
4.Controller Extensions

Visualforce Controllers
1.A Visualforce controller is an Apex class that specifies the data available and the behavior when a user interacts with components on a page.
2.Standard Controllers
- Are provided for all API entities/objects,such as Account,Contact,Opportunity,etc.,as well as custom objects.
- Provide access to standard Salesforce data and behavior.
- Are available to work with record lists.
- Are invlked by using:<apex:page standardController="Contact">

What are Custom Controllers and Controller Extensions?
1.A custom controller is an Apex class that implements all of the logic for a page without leveraging a standard controller. Use custom controllers when you want your Visualforce page to run entirely in system mode, which does not enforce the permissions and field-level security of the current user.
2.A controller extension is an Apex class that extends the functionality of a standard or custom controller. Use controller extensions when:
You want to leverage the built-in functionality of a standard controller but override one or more actions, such as edit, view, save, or delete.
You want to add new actions.
3.You want to build a Visualforce page that respects user permissions. Although a controller extension class executes in system mode, if a controller extension extends a standard controller, the logic from the standard controller does not execute in system mode. Instead, it executes in user mode, in which permissions, field-level security, and sharing rules of the current user apply.

Standard Controllers
1.Standard controllers provide the same common data and functionality and logic used for standard Salesforce pages.
- All standard and custom objects that can be queried using the API have a standard controller.
2.Standard controllers are associated on Visualforce pages using:
- <apex: page standardController="Object">

Standard Controllers
1.Standard controllers include a getter method to return the record specified by the id query string parameter(on the URL).
- This allows the page to access data using the {!object} merge field syntax.
- THis also allows developers to test using URL parameters with known IDs.

Standard Controllers
1.As with API queries, you cna use merge field expression syntax to retrievee data from related records:
- You can traverse up five lvels of child-to-parent relationships.
.Example:{!contact.Account.Owner.FirstName}
-You can traverse down one level of parent-to-child relationships to return an array of all child rows for that parent.
.Example:{!account.Contacts}

Standard Controllers
1.Action methods perform logic or navigation when a page event occurs.
- Action methods are invoked using the {!actionmethod} syntax.
2.Standard controllers define the following actionmethods:
- save ()
- quicksave ()
- edit ()
- delete ()
- cancel ()

Standard List Controllers
1.For almost every standard controller there existent standard list controller that allows you to create pages that display and act on a set of records, such as list page,related list,and mass action pages.
2.To select the standard list controller instead of the regular standard controller,use the recordSetVar attribute on the page tag.
- <apex;page standardController="Account" recordSetVar="accounts">
- This also creates a variable that represents the record set for the page.

Pagination with a List Controller
1.You can add pagination to a page using a list controller by utilizing the next and previous actions. For example, if you create a page with the following markup:

<apex:page standardController="Account" recordSetvar="accounts">
  <apex:pageBlock title="Viewing Accounts">
  <apex:form id="theForm">
    <apex:pageBlockSection >
      <apex:dataList var="a" value="{!accounts}" type="1">
        {!a.name}
      </apex:dataList>
    </apex:pageBlockSection>
    <apex:panelGrid columns="2">
      <apex:commandLink action="{!previous}">Previous</apex:commandlink>
      <apex:commandLink action="{!next}">Next</apex:commandlink>
    </apex:panelGrid>
  </apex:form> 
  </apex:pageBlock>
</apex:page>

Custom Controllers
1.A custom controller is an Apex class that implement all of the logic for a page without leveraging a standard controller.
- Custom controllers typically define three different types of methods:
.Getter methods to retrieve data from the controller.
.Setter methods to pass data from the page to the controller.
.Action Methods to perform logic.
- Navigation action methods to take the usersomewhere else.
- Custom controllers mustexplicitly define all action methods, including those found in standard controllers.

Custom Controllers:Getter Methods
1.Getter methods provide ways to return object data in a Visualforce page.
2.Getter methods take the form:getDataname() which uses the name of the data retrueved.
3.In a Visualforce page, the data can be accessed using the {!Dataname} merge field syntax.

Setter Methods
1.Setter methods pass user-specified values from page markup to a controller. Any setter methods in a controller are automatically executed before any action methods.
2.For example, the following markup displays a page that implements basic search functionality for Leads. The associated controller includes getter and setter methods for the search box input, and then uses the search text to issue a SOSL query when the user clicks Go!. Although the markup doesn’t explicitly call the search text setter method, it executes before the doSearch action method when a user clicks the command button:
<apex:page controller="theController">
   <apex:form>
      <apex:pageBlock mode="edit" id="block">
         <apex:pageBlockSection>
            <apex:pageBlockSectionItem>
               <apex:outputLabel for="searchText">Search Text</apex:outputLabel>
               <apex:panelGroup>
                  <apex:inputText id="searchText" value="{!searchText}"/>
                  <apex:commandButton value="Go!" action="{!doSearch}" 
                                      rerender="block" status="status"/>
               </apex:panelGroup>
            </apex:pageBlockSectionItem>
        </apex:pageBlockSection>
        <apex:actionStatus id="status" startText="requesting..."/>
        <apex:pageBlockSection title="Results" id="results" columns="1">
           <apex:pageBlockTable value="{!results}" var="l" 
                               rendered="{!NOT(ISNULL(results))}">
              <apex:column value="{!l.name}"/>
              <apex:column value="{!l.email}"/>
              <apex:column value="{!l.phone}"/>
           </apex:pageBlockTable>
        </apex:pageBlockSection>
      </apex:pageBlock>
   </apex:form>
</apex:page>

Action Methods
1.Action methods perform logic or navigation when a page event occurs, such as when a user clicks a button, or hovers over an area of the page. Action methods can be called from page markup by using {! } notation in the action parameter of one of 
the following tags:
- <apex:commandButton> creates a button that calls an action
- <apex:commandLink> creates a link that calls an action
- <apex:actionPoller> periodically calls an action
- <apex:actionSupport> makes an event (such as “onclick”, “onmouseover”, and so on) on another, named component, call an action
-<apex:actionFunction> defines a new JavaScript function that calls an action
-<apex:page> calls an action when the page is loaded
2. For example, in the sample page in Building a Custom Controller, the controller's save method is called by the action parameter of the <apex:commandButton> tag. Other examples of action methods are discussed in Defining Action Methods.

Exercise 5-1:Creating a Visualforce Page with a Custom Controller
1.Goal(s):
- Create a Visualforce page to accompany a custom controller
2.Scenario:
- Universal Containers wants to start learning more about controllers,and at the same time create a special search page for candidate information that allows you to search for a candidate by first name,last name,or email all at he same time.
3.Tasks:
- Add the pre-existing Visualforce page to your org.
- Add the controller class.
- Test the page by searching for candidates.