update a field on contact once i associate a account

Question

i wanted to update a field on contact once i associate a account.

once accountcontactrelation is created i am checking if that relation role is Manager and if yes then only i wanted to update a contact field.

My query is how cani achieve this in before trigger .beacuse if i write after trigger then my trigger is calling twice.Please suggest

and in before insert i am not getting any ACR and if on update I change the ACR then still not getting ACR query

map<id,AccountContactRelation>acrmap=new map<id,AccountContactRelation >();

    for(AccountContactRelation acr: [Select id,ContactId,Role__c from AccountContactRelation where (Role__c='Manager) and contactid in:newconMap.keyset() ]) {
        acrmap.put(acr.contactid,acr);
    }

    for(contact con:newconMap.values()) {
        if(acrmap.containsKey(con.id))
            con.isManager__c = true;   
    }     

Answer 1

In the trigger you can check what stage you are in and then only run code when you want it to.

trigger TriggerName on SObjectType (before insert, before update, before delete, after insert, after update, after delete) {

 if (trigger.isBefore){
    if (trigger.isUpdate){
        //run your code here
        //for good practice and readability, call a class that has your code in it
    }
    else if (trigger.isInsert){
    }
    else if (trigger.isDelete){
    }
}
else if (trigger.isAfter){
    if (trigger.isUpdate){
    }
    else if (trigger.isInsert){
    }
    else if (trigger.isDelete){
    }
}