I got null value from component attribute

Question

I got null value for agreementId when I try to type it

Apex Class

public class selectedTasks {
    private final List<agreement__c> agreementTasks;
    public String agreementId {set;get;}

    public agreement__c selectedAgreement {set;get;}
    private String finalQuery = '';

    public selectedTasks() {
        try{
            agreementTasks = [SELECT name FROM agreement__c WHERE Id =:agreementId ];

        } catch(Exception e){
            errorMessage = 'Id : '+agreementId;
        }
    }
}

VF Component

<apex:component controller="selectedTasks" access="global">
    <apex:attribute assignTo="{!agreementId}" 
                    name="agrId" type="String" 
                    description="Agreement ID"
                    access="global"
                    required="true"/>
    {!errorMessage}
</apex:component>

VF Page

<apex:page >
  <c:Partner_Tasks_Component agrId="a0Z25000001cSXG" />
</apex:page>

Answer 1

I have faced similar issues earlier when using components. Seems, we are not able to use {get;set;} when working with components. Please try changing the below line from your code

public String agreementId {set;get;}

to

public String agreementId;

public void setAgreementId(String argId){
agreementId = argId;    
} 

public String getAgreementId(){
return agreementId; 
}

I have done similar changes in my controller and it has worked fine for me. Please see if this works for you too.

Answer 2

Since you're trying to load an agreement record, I would change your class as follows:

public class selectedTasks {
    // Must be public or it won't be useful outside the class
    public Agreement__c agreement { get; set; }
    // Remember the Id in case we need it later.
    Id agreementId;
    public void setAgreementId(Id agreementId) {
        if(this.agreementId == null) {
            this.agreementId = agreementId;
            try {
                agreement = [SELECT Name FROM Agreement__c WHERE Id = :agreementId];
            } catch(QueryException e) {
                // The agreement could not be queried if we got here
            }
        }
    }
}