Bulkify Apex Triggers

This is something that has been harped on in every Apex class I have taken and it finally clicked with me! This is probably much more clearly explained in the link below from developer.force.com but I want to document it here for my own knowledge.

http://wiki.developerforce.com/page/Best_Practice:_Bulkify_Your_Code

• Create a SET before entering trigger.new that will hold the ID of all SObjects being updated or looped through
• Pull a list of the IDs of the SObjects that need to be updated when looping through trigger.new and add them to the SET defined above
• If that SET contains items then create a list of SObjects and use 1 SOQL query to populate the entire list
• Now you can loop through the entire list of SObjects and make updates from there...

Below is an example of this in action:

if(trigger.isBefore){

//Set to hold the list of Contract Id's that will be queried for the associated Account 

Set<String> ContractIds = new Set<String>();

//loop through all Agency Commission Records and add the Id of the Contract to the ContractIds Set

for(Agency_Commission__c ac : trigger.new){

if(ac.Contract__c != null){

ContractIds.add(ac.Contract__c);

}

}

if(!ContractIds.isEmpty()){

//Use a single query to pull a list of Contract SObjects

List<Asset_C__c> contractList = [select id, Account__c from Asset_C__c where id =: ContractIds];

//Map to hold the Contract ID as the Primary Key and the Account ID as the Key Value

Map<string, string> ContractAndAccount = new Map<string, string>();

//Loop through the List of Contracts and add the Contract ID and Account ID to the map

for(Asset_C__c c1 : contractList){

if(c1.Account__c != null){

ContractAndAccount.put(c1.id, c1.Account__c);

}

}

if(!ContractAndAccount.isEmpty()){

//Loop through the original Agency commission values and assign the Account based on the ContractAndAccount Map

for(Agency_Commission__c acUpdate : trigger.new){

//retrieve the Account from the ContractAndAccount Map and assign it to a string value

String acctForContract = ContractAndAccount.get(acUpdate.Contract__c);

acUpdate.Client__c = acctForContract;

}

}

}

}