"A phantom type is a parametrised type whose parameters do not all appear on the right-hand side of its definition..." Haskell Wiki, PhantomType
The following write-up is intended as an introduction into using phantom types in ReasonML.
Taking a look at the above definition from the Haskell wiki, it states that phantom types are parametrised types where not all parameters appear on the right-hand side. Let's try to see if we can implement a similar example as in said wiki.
A maintainable application architecture requires that the UI only contain the rendering logic and execute queries and mutations against the underlying data model on the server. A maintainable architecture must not contain any logic for composing "app state" on the client as that would necessarily embed business logic in the client. App state should be persisted to the database and the client projection of it should be composed in the mid tier, and refreshed as mutations occur on the server (and after network interruption) for a highly interactive, realtime UX.
With GraphQL we are able to define an easy-to-change application-level data schema on the server that captures the types and relationships in our data, and wiring it to data sources via resolvers that leverage our db's own query language (or data-oriented, uniform service APIs) to resolve client-specified "queries" and "mutations" against the schema.
We use GraphQL to dyn
| # lib/tasks/db.rake | |
| namespace :db do | |
| desc "Dumps the database to db/APP_NAME.dump" | |
| task :dump => :environment do | |
| cmd = nil | |
| with_config do |app, host, db, user| | |
| cmd = "pg_dump --host #{host} --username #{user} --verbose --clean --no-owner --no-acl --format=c #{db} > #{Rails.root}/db/#{app}.dump" | |
| end | |
| puts cmd |
| CHECKING_OUT_BRANCH=$3 | |
| OLD_BRANCH=$1 | |
| NEW_BRANCH=$2 | |
| if [ $CHECKING_OUT_BRANCH -eq 1 ] | |
| then | |
| FILES_CHANGED=`git diff $OLD_BRANCH $NEW_BRANCH --name-status` | |
| MIGRATIONS_REMOVED=`echo "$FILES_CHANGED" | egrep 'D\tdb/migrate/([0-9]+)' | sort -r` | |
| MIGRATIONS_ADDED=`echo "$FILES_CHANGED" | egrep 'A\tdb/migrate/([0-9]+)'` | |
