Class: SmartTuple

Inherits:
Object
  • Object
show all
Defined in:
lib/smart_tuple.rb

Overview

SQL condition builder.

tup = SmartTuple.new(" AND ")
tup << {:brand => "Nokia"}
tup << ["min_price >= ?", 75]
tup.compile   # => ["brand = ? AND min_price >= ?", "Nokia", 75]

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(glue, attrs = {}) ⇒ SmartTuple

Initializer.

new(" AND ")
new(" OR ", :brackets => true)



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# File 'lib/smart_tuple.rb', line 26

def initialize(glue, attrs = {})
  @glue = glue
  clear
  attrs.each {|k, v| send("#{k}=", v)}
end

Instance Attribute Details

#args ⇒ Object (readonly)

Array of SQL argument parts.



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# File 'lib/smart_tuple.rb', line 9

def args
  @args
end

#brackets ⇒ Object

Put brackets around statements. true, false or :auto. Default:

:auto



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# File 'lib/smart_tuple.rb', line 14

def brackets
  @brackets
end

#glue ⇒ Object

String to glue statements together.



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# File 'lib/smart_tuple.rb', line 17

def glue
  @glue
end

#statements ⇒ Object (readonly)

Array of SQL statement parts.



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# File 'lib/smart_tuple.rb', line 20

def statements
  @statements
end

Instance Method Details

#+(arg) ⇒ Object

Add a statement, return new object. See #<<.

SmartTuple.new(" AND ") + {:brand => "Nokia"} + ["max_price <= ?", 300]



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# File 'lib/smart_tuple.rb', line 41

def +(arg)
  # Since #<< supports chaining, it boils down to this.
  dup << arg
end

#<<(arg) ⇒ Object

Add a statement, return self.

# Array.
tup << ["brand = ?", "Nokia"]
tup << ["brand = ? AND color = ?", "Nokia", "Black"]

# Hash.
tup << {:brand => "Nokia"}
tup << {:brand => "Nokia", :color => "Black"}

# Another SmartTuple.
tup << other_tuple

# String. Generally NOT recommended.
tup << "min_price >= 75"

Adding anything empty or blank (where appropriate) has no effect on the receiver:

tup << nil
tup << []
tup << {}
tup << another_empty_tuple
tup << ""
tup << "  "     # Will be treated as blank if ActiveSupport is on.



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# File 'lib/smart_tuple.rb', line 70

def <<(arg)
  # NOTE: Autobracketing is placing `[value]` instead of `value` into `@statements`. #compile understands it.

  # Chop off everything empty first time.
  if arg.nil? or (arg.empty? rescue false) or (arg.blank? rescue false)
  elsif arg.is_a? String or (arg.acts_like? :string rescue false)
    @statements << arg.to_s
  elsif arg.is_a? Array
    # NOTE: If arg == [], the execution won't get here.
    #       So, we've got at least one element. Therefore stmt will be scalar, and args -- DEFINITELY an array.
    stmt, args = arg[0], arg[1..-1]
    if not (stmt.nil? or (stmt.empty? rescue false) or (stmt.blank? rescue false))
      # Help do autobracketing later. Here we can ONLY judge by number of passed arguments.
      @statements << (args.size > 1 ? [stmt] : stmt)
      @args += args
    end
  elsif arg.is_a? Hash
    arg.each do |k, v|
      if v.nil?
        # NOTE: AR supports it for Hashes only. ["kk = ?", nil] will not be converted.
        @statements << "#{k} IS NULL"
      else
        @statements << "#{k} = ?"
        @args << v
      end
    end
  elsif arg.is_a? self.class
    # NOTE: If arg is empty, the execution won't get here.

    # Autobrackets here are smarter, than in Array processing case.
    stmt = arg.compile[0]
    @statements << ((arg.size > 1 or arg.args.size > 1) ? [stmt] : stmt)
    @args += arg.args
  else
    raise ArgumentError, "Invalid statement #{arg.inspect}"
  end

  # Return self, it's IMPORTANT to make chaining possible.
  self
end

#add_each(collection, &block) ⇒ Object

Iterate over collection and add block’s result to self once per each record.

add_each(brands) do |v|
  ["brand = ?", v]
end

Can be conditional:

tup.add_each(["Nokia", "Motorola"]) do |v|
  ["brand = ?", v] if v =~ /^Moto/
end

Raises:

  • (ArgumentError) 


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# File 'lib/smart_tuple.rb', line 122

def add_each(collection, &block)
  raise ArgumentError, "Code block expected" if not block

  collection.each do |v|
    self << yield(v)
  end

  # This is IMPORTANT.
  self
end

#clear ⇒ Object

Clear self.



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# File 'lib/smart_tuple.rb', line 144

def clear
  @statements = []
  @args = []
  @brackets = :auto

  # `Array` does it like this. We do either.
  self
end

#compile ⇒ Object Also known as: to_a

Compile self into an array. Empty self yields empty array.

compile   # => []
compile   # => ["brand = ? AND min_price >= ?", "Nokia", 75]



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# File 'lib/smart_tuple.rb', line 157

def compile
  return [] if empty?

  # Build "bracketed" statements.
  bsta = @statements.map do |s|
    auto_brackets, scalar_s = s.is_a?(Array) ? [true, s[0]] : [false, s]

    # Logic:
    #   brackets  | auto  | result
    #   ----------|-------|-------
    #   true      | *     | true
    #   false     | *     | false
    #   :auto     | true  | true
    #   :auto     | false | false

    brackets = if @statements.size < 2
      # If there are no neighboring statements, there WILL BE NO brackets in any case.
      false
    elsif @brackets == true or @brackets == false
      @brackets
    elsif @brackets == :auto
      auto_brackets
    else
      raise "Unknown @brackets value #{@brackets.inspect}, SE"
    end

    if brackets
      ["(", scalar_s, ")"].join
    else
      scalar_s
    end
  end

  [bsta.join(glue)] + @args
end

#empty? ⇒ Boolean

Return true if self is empty.

tup = SmartTuple.new(" AND ")
tup.empty?    # => true

Returns:

  • (Boolean) 


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# File 'lib/smart_tuple.rb', line 198

def empty?
  @statements.empty?
end

#initialize_copy(src) ⇒ Object

Service initializer for dup.



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# File 'lib/smart_tuple.rb', line 33

def initialize_copy(src)    #:nodoc:
  @statements = src.statements.dup
  @args = src.args.dup
end

#size ⇒ Object

Get number of sub-statements.



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# File 'lib/smart_tuple.rb', line 203

def size
  @statements.size
end