This is something extensively used, but every time I need to look for some easy code.
So here is the solution (apologies as I've not covered the negative cases in code, and I hope you all are smart enough to take care of that). Requirement is to build the dynamic page block table with dynamic columns, but this is not it. It should be so dynamic that user can select the object and it's fields by himself and nothing should be hard-coded. So first of all I've provided a picklist with all objects (not all objects... why? Take a look at it Please Remove The System Objects From My sObject List)
Visualforce Page Code:
<apex:page controller="DynamicTableController">
<apex:pageBlock >
<apex:form >
<apex:actionFunction name="ObjectFileds" action="{!ObjectFields}"/>
<apex:commandButton value="Show Table" action="{!ShowTable}"/>
<apex:pageBlockSection >
<apex:pageBlockSectionItem >
<apex:outputLabel value="Select Object"/>
<apex:selectList multiselect="false" size="1" value="{!SelectedObject}" onchange="ObjectFileds();">
<apex:selectOption itemLabel="--None--" itemValue="--None--"/>
<apex:selectoptions value="{!supportedObject}" />
</apex:selectlist>
</apex:pageBlockSectionItem>
<apex:pageBlockSectionItem >
<apex:outputLabel value="Select Field"/>
<apex:selectList multiselect="true" size="5" value="{!SelectedFields}">
<apex:selectOption itemLabel="--None--" itemValue="--None--"/>
<apex:selectoptions value="{!fieldLableAPI}" />
</apex:selectlist>
</apex:pageBlockSectionItem>
<apex:pageBlockTable rendered="{!IF(ObjectList.size > 0 , true , false)}" value="{!ObjectList}" var="rec">
<apex:column value="{!rec.Id}" rendered="{!IF(SelectedFields.size == 0 , true, false)}"/>
<apex:repeat value="{!SelectedFields}" var="FieldLable">
<apex:column value="{!rec[FieldLable]}" rendered="{!IF(FieldLable != '--None--' , true, false)}"/>
</apex:repeat>
</apex:pageBlockTable>
<apex:outputPanel rendered="{!IF(ObjectList.size < 1 , true , false)}">
<apex:pageMessage severity="ERROR" summary="No records to display"/>
</apex:outputPanel>
</apex:pageBlockSection>
</apex:form>
</apex:pageBlock>
</apex:page>
Apex Code (Class):
public class DynamicTableController
{
//List displayed on UI
public List<selectoption> supportedObject {get; set;}
//Selected Object
public String SelectedObject {get; set;}
//Global describe
Map<String, Schema.SObjectType> gd = Schema.getGlobalDescribe();
Set<String> objectKeys = gd.keySet();
//Field Select List
public List<SelectOption> fieldLableAPI {get; set;}
//Selected fields to be displayed in table
public List<String> SelectedFields {get; set;}
//List to maintain dynamic query result
public List<sObject> ObjectList {get; set;}
//Constructor
public DynamicTableController()
{
//Initialize
supportedObject = new List<selectoption>() ;
SelectedObject = '' ;
fieldLableAPI = new List<SelectOption>() ;
SelectedFields = new List<String>() ;
ObjectList = new List<sObject>() ;
//Get only reference to objects
for(Schema.SObjectType item : ProcessInstance.TargetObjectId.getDescribe().getReferenceTo())
{
//Excluding custom setting objects
if(!item.getDescribe().CustomSetting)
{
//Adding to list
supportedObject.add(new SelectOption(item.getDescribe().getLocalName().toLowerCase() , item.getDescribe().getLabel() ));
}
}
}
//Get fields of selected object
public void ObjectFields()
{
if(SelectedObject != '--None--')
{
//Creating sObject for dynamic selected object
Schema.SObjectType systemObjectType = gd.get(SelectedObject);
//Fetching field results
Schema.DescribeSObjectResult r = systemObjectType.getDescribe();
Map<String, Schema.SObjectField> M = r.fields.getMap();
//Creating picklist of fields
for(Schema.SObjectField fieldAPI : M.values())
{
fieldLableAPI.add(new SelectOption(fieldAPI.getDescribe().getName() , fieldAPI.getDescribe().getLabel())) ;
}
}
}
public void ShowTable()
{
//Creating dynamic query with selected field
String myQuery = 'Select Id ' ;
for(String field : SelectedFields)
{
if(field.toLowerCase() != 'id' && field.toLowerCase() != '--none--')
myQuery += ','+ field + ' ' ;
}
//Limit is 100 for now you can change it according to need
myQuery += ' from ' + SelectedObject + ' LIMIT 100' ;
//Executing the query and fetching results
ObjectList = Database.query(myQuery) ;
}
}
Once user selects any object from the first picklist, filed picklist will be populated with all the field labels related to that object. Note, it's a multi-select picklist so user can select multiple fields. Once fields are selected and "Show Table" is clicked, page block table will display the field values (selected in field picklist) of all records (limit is 100 right now, you can change it according to your need).
There are some extra checks that needs to be implemented in code like "isQueryable" etc..
Amit Jain
