Customer details specification
Create a new file for the specifications, src/practicalli/banking_specifications.cljc, with the namespace practicalli.banking-specifications.
Require the clojure.spec.alpha library with an alias of spec.
(ns practicalli.banking-specifications
(:require [clojure.spec.alpha :as spec]))
Define basic customer details
Define a specification for the customer-details map, composed of all the required keys that define a customer.
The bank legally requires specific information about a customer in order to add them as an account holder
(spec/def ::first-name string?)
(spec/def ::last-name string?)
(spec/def ::email-address string?)
A more detailed email specification
A residential address is made from several pieces of information and is defined as a composite specification, from several specifications.
(spec/def ::house-name-number (spec/or :string string?
:number int?))
(spec/def ::street-name string?)
(spec/def ::post-code string?)
(spec/def ::county string?)
(spec/def ::country string?)
(spec/def ::residential-address (spec/keys :req [::house-name-number ::street-name ::post-code]
:opt [::county ::country]))
A social security number specification is also a candidate for a composite specification. Social security numbers may take different forms and even have different names in different countries, eg. the USA SSN is a nine-digit number in the format "AAA-GG-SSSS"
In the UK the social security number is called the National Insurance number and is of the form QQ123456C
(spec/def ::social-security-id-uk string?)
(spec/def ::social-security-id-usa string?)
Detailed social security numbers would check the different forms
Predicate functions can be defined to check for the size of the different social security forms.
(defn social-security-number-usa? [value] (= 9 (count value)))
(defn social-security-number-uk? [value] (= 11 (count value)))
(spec/def ::social-security-id-usa (spec/and string? social-security-number-usa?))
(spec/def ::social-security-id-uk (spec/and string? social-security-number-uk?))
These specifications required a custom generator in order to produce correct data each time.
A general social security specification can now be defined, with one of any of the country specific specifications
(spec/def ::social-security-id (spec/or ::social-security-id-uk
::social-security-id-usa))
Composing the customer details specification
A customer details specification is a hash-map of key value pairs. The keys are the specifications that have just been defined.
spec/keys creates a specification for a hash-map with required and optional keys. spec/keys also includes a check for a map, so no explicit check for a map is required.
(spec/def ::customer-details
(spec/keys
:req [::first-name ::last-name ::email-address ::residential-address ::social-security-id]))