How to do it...

We will load data from a .csv file containing records customers, and we will instantiate a new class instance for each record. These records will be added to a list.

1. Import the R6 library:

library(R6)

1. Load the data from a .csv file:

customers = read.csv("./Customers_data.csv")

1. We will now begin defining the R6Class structure. Note that we have two lists, one for the public attributes or methods, and another one for the private (these methods or attributes can only be accessed by other methods from this class). The initialize method is called whenever we create a new instance of this class. Note that we refer to the internal elements from this class using the self$ notation:

Customer = R6Class(public=list(Customer_id = NULL,Name = NULL,City = NULL,
initialize = function(customer_id,name,city,Missing_product,Missing_since){
 self$Customer_id <- customer_id
 self$Name <- name
 self$City <- city
},
is_city_in_america = function(){
 return (upper_(self$City) %in% c("NEW YORK","LONDON","MIAMI","BARCELONA"))
},
full_print = function(){
 print("------------------------------------")
 print(paste("Customer name ->",self$Name))
 print(paste("Customer city ->",self$City))
 print("------------------------------------")
}
),private=list(
upper_ = function(x){
 return (toupper(x))
}
))

1. We loop through our DataFrame and create a new Customer instance, passing three arguments. These are passed to the initialize method that we defined previously:

list_of_customers = list()
for (row in 1:nrow(customers)){
 row_read = customers[row,]
 customer = Customer$new(row_read$Customer_id,row_read$Name,row_read$City)
 list_of_customers[[row]] <- (customer)
}

1. We call our print method:

list_of_customers[[1]]$full_print()

The following screenshot prints the customer name and city: