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tulasiram chtulasiram ch 

Initial term of field expression must be a concrete SObject: List<Position__c>

Why i am getting this error , and what it wants to tell me exactly...
trigger duplicateTriggeronPosition on Position__c (before insert, before update) {
    for(Position__c pos:Trigger.new){    
    List<Position__c> posRec=[select id from Position__c where Name=:pos.Name];
        if(posRec.size()>0){
            posRec.Name.addError('You Are entering duplicate name');
        }
}
}
Best Answer chosen by tulasiram ch
Abhishek_DEOAbhishek_DEO
You are using addError() method on a LIST, however, it should be use for object only i.e. on List element. Also, you should not place the query inside FOR loop

 posRec.Name.addError('You Are entering duplicate name'); // this is incorrect

Below code might work for you.Here "posRec" is an object. in you old code , you might use

posRec[0].Name.addError('You Are entering duplicate name');
 
trigger duplicateTriggeronPosition on Position__c (before insert, before update) {
    set<string> firstname = new set<string>();
	for(Position__c pos:Trigger.new){
		firstname.add(pos.Name);
    }
	for(Position__c posRec : [select id from Position__c where Name=:firstname]){
		posRec.Name.addError('You Are entering duplicate name');
	}
}


Please let me know if it helps you.
 

All Answers

Abhishek_DEOAbhishek_DEO
You are using addError() method on a LIST, however, it should be use for object only i.e. on List element. Also, you should not place the query inside FOR loop

 posRec.Name.addError('You Are entering duplicate name'); // this is incorrect

Below code might work for you.Here "posRec" is an object. in you old code , you might use

posRec[0].Name.addError('You Are entering duplicate name');
 
trigger duplicateTriggeronPosition on Position__c (before insert, before update) {
    set<string> firstname = new set<string>();
	for(Position__c pos:Trigger.new){
		firstname.add(pos.Name);
    }
	for(Position__c posRec : [select id from Position__c where Name=:firstname]){
		posRec.Name.addError('You Are entering duplicate name');
	}
}


Please let me know if it helps you.
 
This was selected as the best answer
Dayakar.DDayakar.D
Hi tulasiram ch,
Please try this,it may solve your problem,
trigger duplicateTriggeronPosition on Position__c  (before insert, before update) {
    set<string> firstname = new set<string>();
	for(Position__c  pos:Trigger.new){
		firstname.add(pos.Name);
    }
list<Position__c > listOfPositions=[select id from Position__c  where Name in :firstname];
if(listOfPositions.size()>0)
{
for(Position__c  pos:Trigger.new){
		pos.addError('You Are entering duplicate name');
    }
}
}
Regards,
Dayakar
 
Amit Chaudhary 8Amit Chaudhary 8
Never use SOQL inside for loop
Please try below code.
trigger duplicateTriggeronPosition on Position__c  (before insert, before update) 
{
	set<string> firstname = new set<string>();
	set<Id> setOppId = new Set<Id>();
	
	for(Position__c  pos:Trigger.new)
	{
		firstname.add(pos.Name);
		setOppId.add(pos.id);
	}

	list<Position__c > listOfPositions=[select id,Name from Position__c  where Name in :firstname and id not in : setOppId ];
	
	Map<String,Position__c> mapNamewisePost =  new Map<String,Position__c>();
	for(Position__c pos : listOfPositions)
	{
		mapNamewisePost.put(pos.Name , pos);
	}
	
	for(Position__c  pos:Trigger.new)
	{
		if(mapNamewisePost.containsKey(pos.Name))
		{
			pos.Name.addError('You Are entering duplicate name');
		}
	}
}
1) http://amitsalesforce.blogspot.com/2015/06/trigger-best-practices-sample-trigger.html

1) One Trigger Per Object
A single Apex Trigger is all you need for one particular object. If you develop multiple Triggers for a single object, you have no way of controlling the order of execution if those Triggers can run in the same contexts

2) Logic-less Triggers
If you write methods in your Triggers, those can’t be exposed for test purposes. You also can’t expose logic to be re-used anywhere else in your org.

3) Context-Specific Handler Methods
Create context-specific handler methods in Trigger handlers

4) Bulkify your Code
Bulkifying Apex code refers to the concept of making sure the code properly handles more than one record at a time.

5) Avoid SOQL Queries or DML statements inside FOR Loops
An individual Apex request gets a maximum of 100 SOQL queries before exceeding that governor limit. So if this trigger is invoked by a batch of more than 100 Account records, the governor limit will throw a runtime exception

6) Using Collections, Streamlining Queries, and Efficient For Loops
It is important to use Apex Collections to efficiently query data and store the data in memory. A combination of using collections and streamlining SOQL queries can substantially help writing efficient Apex code and avoid governor limits

7) Querying Large Data Sets
The total number of records that can be returned by SOQL queries in a request is 50,000. If returning a large set of queries causes you to exceed your heap limit, then a SOQL query for loop must be used instead. It can process multiple batches of records through the use of internal calls to query and queryMore

8) Use @future Appropriately
It is critical to write your Apex code to efficiently handle bulk or many records at a time. This is also true for asynchronous Apex methods (those annotated with the @future keyword). The differences between synchronous and asynchronous Apex can be found

9) Avoid Hardcoding IDs
When deploying Apex code between sandbox and production environments, or installing Force.com AppExchange packages, it is essential to avoid hardcoding IDs in the Apex code. By doing so, if the record IDs change between environments, the logic can dynamically identify the proper data to operate against and not fail