Expressions

Expressions evaluate into useful objects via a query builder like interface.

Expressions provides an API for expression types. You can build your own Expression, or use expressions created via the gems below:

Type Expression

# Via method definition:
def method(my_var: MyType); end

# Via type() helper:
my_var = type MyType | fetch_my_object(id: 123)

my_var is now type checked to be of type MyType when assigned to.

ℹ️ Requires: LowType

Dependency Expression

def method(my_var: Dependency); end

my_var is now automatically assigned to via dependency injection.

ℹ️ Requires: LowType and LowDependency

Data Expression [UNRELEASED]

The table expression inverts the usual database query logic. Instead of building a query of what we want from the database, we build the table we want and let the expression build the query.

table(:username > :title | :body)

The above expression builds a ORM query to right join the user table into the articles table and results in a list of articles with the user's username in each row

ℹ️ Requires: LowData

API

Inherit from Expressions::Expression and define a hook/callback:

Hook / callback method	Trigger
`def union_expression(expression)`	`MyExpression \| MyExpression[]`
`def union_value(value)`	`MyExpression \| :my_value`
`def union_type(type)`	`MyExpression \| MyType`
`def gt_expression(expression)`	`MyExpression > MyExpression[]`
`def gt_value(value)`	`MyExpression > :my_value`
`def gt_type(type)`	`MyExpression > MyType`
`def gt_or_et_expression(expression)`	`MyExpression >= MyExpression[]`
`def gt_or_et_value(value)`	`MyExpression >= :my_value`
`def gt_or_et_type(type)`	`MyExpression >= MyType`
`def lt_expression(expression)`	`MyExpression < MyExpression[]`
`def lt_value(value)`	`MyExpression < :my_value`
`def lt_type(type)`	`MyExpression < MyType`
`def lt_or_et_expression(expression)`	`MyExpression <= MyExpression[]`
`def lt_or_et_value(value)`	`MyExpression <= :my_value`
`def lt_or_et_type(type)`	`MyExpression <= MyType`

Installation

Gems using Expressions will do this step for you, but if you'd like to build your own expression then add gem 'expressions' to your Gemfile and run:

bundle install