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DBManagerDBManager 

Display <div> element if value in string set

My company runs events and sells stands at those events, and I would like to implement a feature which allows the sales teams to see which stands have been sold and which haven't. However, given that I am still trying to learn Visualforce and Apex through trial and error, I am finding it difficult to implement the 'reserved or vacant' part of this solution.

 

So far I have a visualforce page where the background is set to an image of the venue floorplan. Each stand is overlayed with a <div> element, where the background image of the <div> is a red diagonal line with a transparent background (indicating that stand is reserved).

 

So the code looks something like this:

<apex:page renderAs="pdf" standardController="Issue_Year__c" extensions="FloorplanSet">

<head>
<style type="text/css"> 
@page {
size: A4 landscape;
}

body {
background-image:url("https://c.cs2.content.force.com/servlet/servlet.FileDownload?file=015R0000000AdVD");
background-repeat:no-repeat;
}

.med {
position:absolute;
float:left;
background-image:url("https://c.cs2.content.force.com/servlet/servlet.FileDownload?file=015R0000000Ae5R");
background-repeat:no-repeat;
height:20px;
width:20px;
}

</style>
</head>

<body>

<div style="position:relative;">
<div id="60" class="med" style="top:8.54cm; left:7.05cm;"></div>
</div

</body>

 

Obviously, I only want the red diagonal line to display when the stand number is reserved, so I need an Apex Class to get the list of reserved stands. I can then check if each stand number is in the list, and change the visibility of each <div> accordingly.

 

This class currently looks like this:

public class FloorplanSet {

private final Issue_Year__c evis;
private Set<String> stand;

public FloorplanSet(ApexPages.StandardController stdController) {
    this.evis = (Issue_Year__c)stdController.getRecord();
}

public Set<String> getStand() {
    for (Stand__c sta :[SELECT Name FROM Stand__c WHERE Event_Issue__c = :evis.Id AND Status__c = 'Reserved']){
        stand.add(sta.Name);
    }
    return stand;
}

}

 

What I am having difficulty doing is retrieving the list of stand numbers ({!stand}) and seeing if the stand number for each <div> (which is also the id for the div, i.e. '60') is present in that list.

 

For testing purposes, I have tried simply adding {!stand} into the Visualforce page, and though it saves, I get the following error when I try to load the page:

common.apex.runtime.impl.ExecutionException: Attempt to de-reference a null object 

 

Hope someone can help.

Best Answer chosen by Admin (Salesforce Developers) 
DBManagerDBManager

I've only gone and done it!

 

Visualforce:

<apex:page renderAs="pdf" standardController="Issue_Year__c" extensions="FloorplanSet">

<head>
<style type="text/css"> 
@page {
size: A4 landscape;
}

body {
background-image:url("https://c.cs2.content.force.com/servlet/servlet.FileDownload?file=015R0000000AdVD");
background-repeat:no-repeat;
}

.med {
position:absolute;
float:left;
background-image:url("https://c.cs2.content.force.com/servlet/servlet.FileDownload?file=015R0000000Ae5R");
background-repeat:no-repeat;
height:20px;
width:20px;
}

</style>
</head>

<body>

<apex:variable var="s" value="{!stand}"/>

<div style="position:relative;">
<div id="60" class="med" style="top:8.54cm; left:7.05cm; display:{!IF(CONTAINS(s,'60'),'block','none')};"></div>
</div>

 

Apex:

public class FloorplanSet {

private final Issue_Year__c evis;
private String stand;

public FloorplanSet(ApexPages.StandardController stdController) {
    this.evis = (Issue_Year__c)stdController.getRecord();
}

public String getStand() {
    for (Stand__c sta :[SELECT Name FROM Stand__c WHERE Event_Issue__c = :evis.Id AND Status__c = 'Reserved']){
        stand = stand + '/' + sta.Name;
    }
    return stand;
}

}