I need to update all Contact Fields dynamically , I am trying throught Schema.SObjectType but getting some Error

Question

I need to update all contact records from one record to another record which has 333 fields. It takes time to update this. I thought of updating the sobject field dynamically, but I'm getting "Variable does not exist: fieldvalue" while saving the class.

Map<String, Schema.SObjectType> m = Schema.getGlobalDescribe();
Contact existingContact;
List<Schema.SObjectField> fieldsList = new List<Schema.SObjectField>();
Schema.SObjectType s = m.get('Contact');
Schema.DescribeSObjectResult r = s.getDescribe();
Map<String,Schema.SObjectField> fields = r.fields.getMap();
for(Contact con : ConList)
{
    for(Schema.SObjectField fieldItems : fields.values()) {
        Schema.DescribeFieldResult dfield = fieldItems.getDescribe();
        if (dfield.isCreateable() && !dfield.isCalculated()) {
            
            if(con.Id != existingContact.Id)
            {
                
                existingContact.fieldItems = String.isNotBlank(con.fieldItems ) ? con.fieldItems : existingContact.fieldItems ;
            }
        }
    }
}

How can it resolved?

Answer 1

Replace this line:

existingContact.fieldvalue= String.isNotBlank(con.fieldvalue) ? con.fieldvalue : existingContact.fieldvalue;

with:

String f = dfield.getName();
if (String.isNotBlank(con.get(f))) {
    existingContact.put(f, con.get(f));
}

or better:

SObjectField f = fieldItems;
if (String.isNotBlank(con.get(f))) {
    existingContact.put(f, con.get(f));
}

because the SObjectField can be used directly as Apex has map-like syntax for dynamic access of SObject fields. See the SObject Class documentation.

(JavaScript does offer the syntax you used.)

I also removed the assignment of the existingContact value to itself as that seems pointless.

Note that doing this dynamically will likely be slower at runtime than hard coding the field values. But it does have the advantage of getting the set of fields right in the first place and automatically adapting when fields are added. If the fields are unlikely to change in the future, and performance is really important, you could run similar code to this in the Developer Console and output the field API names and hard code those in this logic.