Functional Tools for Salesforce

Functional programming has really not been a thing on the Salesforce platform. However since functional programming is awesome and is becoming more and more popular, here is a library which allows us to do some sort of functional programming in apex. This is work in progress at the moment. Of course all this would've been easier if Apex supported Generic fully, and if it supported passing functions as arguments or even anonymous classes.

Usage - FuncTools class

This is a class containing the basic map, reduce and filter functions and can be used with any standard List.

• Map Function

private class Callback implements FunctionalInterface {
    public Object execute(Object o) {
        Account a = (Account)o;
        a.Name = a.Name + 'A';
        return a;
    }
}
    
List<Account> arr = new List<Account> {
    new Account(name='A'), 
    new Account(name='B')
};

List<Object> result = FuncTools.mapper(arr, new Callback());       
System.assertEquals(2, result.size());
System.assertEquals('AA', ((Account)result[0]).Name);
System.assertEquals('BA', ((Account)result[0]).Name);

• Filter Function

private class Callback implements FunctionalInterface {
    public Object execute(Object o) {
        return Math.mod((Integer) o, 2) == 0;
    }
}

List<Integer> ints = new List<Integer> {1, 2, 3, 4};
                
List<Object> result = FuncTools.filter(ints, new Callback());

System.assertEquals(2, result.size());
System.assertEquals(2, (Integer)result[0]);
System.assertEquals(4, (Integer)result[1]);

• Reduce Function

private class Callback implements FunctionalInterface2 {
    public Object execute(Object acc, Object i) {
        return (Integer)acc + (Integer)i;
    }
}

List<Integer> ints = new List<Integer>{1, 2, 3, 4};
Object result = FuncTools.reduce(ints, new Callback(), 0);

System.assertEquals(10, (Integer) result);

Usage - FList class

This is a wrapper immutable class which provides a better syntax for Lists.

Here is an example:

private class NumbersGreaterThan2 implements FunctionalInterface {
    public Object execute(Object o) {
        return (Integer)o > 2;
    }
}
    
private class DoubleNumbers implements FunctionalInterface {
    public Object execute(Object o) {
        return (Integer)o * 2;
    }
}
    
private class Sum implements FunctionalInterface2 {
    public Object execute(Object o1, Object o2) {
        return (Integer)o1 + (Integer)o2;
    }
}

FList l = new FList(new List<Integer> {1, 2, 3, 4});
Object result = l.filter(new NumbersGreaterThan2())
                 .mapper(new DoubleNumbers())
                 .reduce(new Sum(), 0);
        
System.assertEquals(14, (Integer)result);

The class contains the following methods

• constructor - Pass in a List of Objects to create a FList
• add(Object) - Creates a new FList by cloning the old list and adding the item
• get(Integer) - Gets the element at the index
• cloneList() - Returns a clone of the list
• mapper(FunctionalInterface f) - Returns a new FList and runs the mapping function
• filter(FunctionalInterface f) - Returns a new FList and runs the filtering function
• reduce(FunctionalInterface2 f, Object initialValue) - Returns an object by running the reducing function for each element of the list
• head() - Returns the first element in the list
• tail() - Returns a new FList with every element except for the first one

Usage - SOList class

This is a wrapper immutable class which provides a better syntax for Lists of sObjects.

Here is an example:

Object result = SOList.create([SELECT Id, Name, isActive FROM Account])
                 .filter(new AccountsStartingWithA())
                 .mapper(new SetActiveToFalse())
                 .update();        

or

Map<Id, sObject> result = SOList.create('SELECT Id, Name, isActive FROM Account')
                 .filter(new AccountsStartingWithA())
                 .mapper(new SetActiveToFalse())
                 .update()
                 .errors();

or

Map<Id, sObject> result = SOList.create(Trigger.New)
                 .filter(new AccountsWithChangedNames(Trigger.OldMap))
                 .mapper(new CreateActivitiesForAccounts())
                 .insert()
                 .errors();

The class contains the following methods

• create(ListOfsObjects) or create(QueryString) - A factory class which creates an instance of SOList;
• add(Object) - Creates a new SOList by cloning the old list and adding the item
• get(Integer) - Gets the element at the index
• cloneList() - Returns a clone of the list
• mapper(FunctionalInterface f) - Returns a new SOList and runs the mapping function
• filter(FunctionalInterface f) - Returns a new SOList and runs the filtering function
• reduce(FunctionalInterface2 f, Object initialValue) - Returns an object by running the reducing function for each element of the list
• insert() - Inserts the objects to the database
• update() - Updates the objects into the database
• delete() - Deletes the objects from the database
• errors() - Returns a map of errors created during the operations in the chain