Records in F#

Records in F# are similar to objects in OOP languages. They can have named fields and other members. However, like many other elements in F#, they are immutable.

Here’s how to declare a record of type Book with a couple of fields and a function:

type Book = {
    title: string;
    numberOfPages:int;
    author: string
} 
with member this.takesLongTimeToRead = this.numberOfPages > 500

Here’s how we can declare a new Book:

let myBook = {title = "F# for beginners"; numberOfPages = 600; author = "John Smith"}

We didn’t need to declare its type explicitly.

We can access the record members with the dot notation:

printfn "Book title: %s" myBook.title
let longTimeOrNot = myBook.takesLongTimeToRead

Book title: F# for beginners

val myBook : Book = {title = “F# for beginners”;
numberOfPages = 600;
author = “John Smith”;}
val longTimeOrNot : bool = true

View all F# related articles here.

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About Andras Nemes
I'm a .NET/Java developer living and working in Stockholm, Sweden.

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