Class: ROM::SQL::Attribute

Inherits:
ROM::Schema::Attribute
  • Object
show all
Defined in:
lib/rom/sql/attribute.rb

Overview

Extended schema attributes tailored for SQL databases

Constant Summary collapse

QualifyError =

Error raised when an attribute cannot be qualified

Class.new(StandardError)

Instance Method Summary collapse

Dynamic Method Handling

This class handles dynamic methods through the method_missing method

#method_missing(meth, *args, &block) ⇒ Object (private)

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.

Delegate to sql expression if it responds to a given method



209
210
211
212
213
214
215
 
# File 'lib/rom/sql/attribute.rb', line 209

def method_missing(meth, *args, &block)
  if sql_expr.respond_to?(meth)
    meta(sql_expr: sql_expr.__send__(meth, *args, &block))
  else
    super
  end
end

Instance Method Details

#aliased(name) ⇒ SQL::Attribute Also known as: as

Return a new attribute with an alias

Examples:

users[:id].aliased(:user_id)

Returns:



23
24
25
 
# File 'lib/rom/sql/attribute.rb', line 23

def aliased(name)
  super.meta(sql_expr: sql_expr.as(name))
end

#canonical ⇒ Object

Return a new attribute in its canonical form



31
32
33
34
35
36
37
 
# File 'lib/rom/sql/attribute.rb', line 31

def canonical
  if aliased?
    meta(alias: nil, sql_expr: nil)
  else
    self
  end
end

#concat(other, sep = ' ') ⇒ SQL::Function

Create a CONCAT function from the attribute

Examples:

with default separator (‘ ’)

users[:id].concat(users[:name])

with custom separator

users[:id].concat(users[:name], '-')

Parameters:

Returns:



180
181
182
 
# File 'lib/rom/sql/attribute.rb', line 180

def concat(other, sep = ' ')
  Function.new(type).concat(self, sep, other)
end

#foreign_key ⇒ SQL::Attribute

Return a new attribute marked as a FK

Returns:



106
107
108
 
# File 'lib/rom/sql/attribute.rb', line 106

def foreign_key
  meta(foreign_key: true)
end

#func(&block) ⇒ SQL::Function

Create a function DSL from the attribute

Examples:

users[:id].func { int::count(id).as(:count) }

Returns:



163
164
165
 
# File 'lib/rom/sql/attribute.rb', line 163

def func(&block)
  ProjectionDSL.new(name => self).call(&block).first
end

#is(other) ⇒ Object

Return a boolean expression with ‘=` operator

Examples:

users.where { id.is(1) }

users.where(users[:id].is(1))

Parameters:

  • other (Object) —

    Any SQL-compatible object type



151
152
153
 
# File 'lib/rom/sql/attribute.rb', line 151

def is(other)
  Sequel::SQL::BooleanExpression.new(:'=', self, other)
end

#joined ⇒ SQL::Attribute

Return a new attribute marked as joined

Whenever you join two schemas, the right schema’s attribute will be marked as joined using this method

Returns:



67
68
69
 
# File 'lib/rom/sql/attribute.rb', line 67

def joined
  meta(joined: true)
end

#joined? ⇒ Boolean

Return if an attribute was used in a join

Examples:

schema = users.schema.join(tasks.schema)

schema[:id, :tasks].joined?
# => true

Returns:

  • (Boolean) 


82
83
84
 
# File 'lib/rom/sql/attribute.rb', line 82

def joined?
  meta[:joined].equal?(true)
end

#qualified ⇒ SQL::Attribute

Return a new attribute marked as qualified

Examples:

users[:id].aliased(:user_id)

Returns:



47
48
49
50
51
52
53
54
55
56
57
 
# File 'lib/rom/sql/attribute.rb', line 47

def qualified
  return self if qualified?

  case sql_expr
  when Sequel::SQL::AliasedExpression, Sequel::SQL::Identifier
    type = meta(qualified: true)
    type.meta(qualified: true, sql_expr: Sequel[type.to_sym])
  else
    raise QualifyError, "can't qualify #{name.inspect} (#{sql_expr.inspect})"
  end
end

#qualified? ⇒ Boolean

Return if an attribute type is qualified

Examples:

id = users[:id].qualify

id.qualified?
# => true

Returns:

  • (Boolean) 


97
98
99
 
# File 'lib/rom/sql/attribute.rb', line 97

def qualified?
  meta[:qualified].equal?(true)
end

#sql_literal(ds) ⇒ Object

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.

Sequel calls this method to coerce an attribute into SQL string

Parameters:

  • (Sequel::Dataset) 


189
190
191
192
193
194
195
 
# File 'lib/rom/sql/attribute.rb', line 189

def sql_literal(ds)
  if sql_expr
    sql_expr.sql_literal(ds)
  else
    Sequel[to_sym].sql_literal(ds)
  end
end

#to_sym ⇒ Symbol

Return symbol representation of an attribute

This uses convention from sequel where double underscore in the name is used for qualifying, and triple underscore means aliasing

Examples:

users[:id].qualified.to_sym
# => :users__id

users[:id].as(:user_id).to_sym
# => :id___user_id

users[:id].qualified.as(:user_id).to_sym
# => :users__id___user_id

Returns:

  • (Symbol) 


128
129
130
131
132
133
134
135
136
137
138
139
 
# File 'lib/rom/sql/attribute.rb', line 128

def to_sym
  @_to_sym ||=
    if qualified? && aliased?
      :"#{source.dataset}__#{name}___#{meta[:alias]}"
    elsif qualified?
      :"#{source.dataset}__#{name}"
    elsif aliased?
      :"#{name}___#{meta[:alias]}"
    else
      name
    end
end