Force.com 云计算平台试玩小结（三）-优快云博客

本文通过实例展示了如何使用Apex编写业务逻辑，包括触发器的定义与更新产品价格时的相关操作。同时介绍了如何利用Visualforce创建定制化的用户界面，并通过Force.com Sites发布公共网页。

最大的不便：只能用Flash Builder 4构建基于桌面的AIR程序，基于Web的Flex应用暂时还不支持。。。

Tutorial #5: Adding Business Logic with Apex

Apex是运行在Force.com上强类型，面向对象的编程语言。
你可以用Apex来编写触发器（trigger）、web services 和 program controllers 。
可以用Apex来编写一些复杂的事务逻辑。
商品（Merchandise）price降低的时候，Invoice Statement 和 Line Item会作出相应的变化。
Setup->Create->Objects->Triggers->New

Step 2: Define a List Variable

trigger HandleProductPriceChange on Merchandise__c (after update) {
    List<Line_Item__c> openLineItems =
    [SELECT j.Unit_Price__c, j.Merchandise__r.Price__c
        FROM Line_Item__c j
        WHERE j.Invoice_Statement__r.Status__c = 'Negotiating'
        AND j.Merchandise__r.id IN :Trigger.new
        FOR UPDATE];
        
    for (Line_Item__c li: openLineItems) {
    if ( li.Merchandise__r.Price__c < li.Unit_Price__c ){
        li.Unit_Price__c = li.Merchandise__r.Price__c;
        }
    }
    update openLineItems;
}

Tutorial #7: Building a Custom User Interface Using Visualforce

Step 1: Enable Visualforce Development Mode

Setup->My Personal Information->Personla Information->Edit->Development Mode

Step 2: Create a Visualforce Page

https://na1.salesforce.com/apex/CountSheet

Tutorial #8: Creating a Public Web Page Using Force.com Sites

Step 1: Create a Product Catalog Page

Setup->Develop->Pages

<apex:page standardstylesheets="false" showHeader="false" sidebar="false" standardController="Merchandise__c" recordSetVar="products" >
<apex:stylesheet value="{!URLFOR($Resource.styles, 'styles.css')}"/>
    <h1>Merchandise Catalog</h1>
    <apex:datatable value="{!products}" var="pitem" rowClasses="odd,even">
        <apex:column headerValue="Product">
            <apex:outputtext value="{!pitem.name}" />
        </apex:column>
        <apex:column headerValue="Description">
            <apex:outputField value="{!pitem.Description__c}"/>
        </apex:column>
        <apex:column headerValue="Price">
            <apex:outputField value="{!pitem.Price__c}"/>
        </apex:column>
    </apex:datatable>
</apex:page>

Step 2: Register a Force.com Domain Name

Setup->Develop->Sites->Register My Force.com Domain->Public Access Settings->Edit->Read permission for the Merchandise object