Class: Cascading::ExprStub

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

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(expression) ⇒ ExprStub

ExprStub requires a Janino expression decorated with field types. For example: ‘“Found: ” + (x:int + y:int) + “ ” + z:string’. Type names are defined in Cascading::JAVA_TYPE_MAP.



8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
 
# File 'lib/cascading/expr_stub.rb', line 8

def initialize(expression)
  @input_expression = expression
  @expression = expression.dup
  @types = {}

  # Simple regexp based parser for types

  JAVA_TYPE_MAP.each do |sym, klass|
    @expression.gsub!(/[A-Za-z0-9_]+:#{sym.to_s}/) do |match|
      name = match.split(/:/).first.gsub(/\s+/, "")
      @types[name] = klass
      match.gsub(/:#{sym.to_s}/, "")
    end
  end
end

Instance Attribute Details

#expression ⇒ Object

Returns the value of attribute expression.



3
4
5
 
# File 'lib/cascading/expr_stub.rb', line 3

def expression
  @expression
end

#input_expression ⇒ Object

Returns the value of attribute input_expression.



3
4
5
 
# File 'lib/cascading/expr_stub.rb', line 3

def input_expression
  @input_expression
end

#types ⇒ Object

Returns the value of attribute types.



3
4
5
 
# File 'lib/cascading/expr_stub.rb', line 3

def types
  @types
end

Class Method Details

.expr(expression, params = {}) ⇒ Object

Convenience constructor for an ExprStub that optionally performs validation. Takes a string to use as a Janino expression and an optional params hash. By default, the param :validate is set to true (performs expression validation using default actual argument values) and the param :validate_with is set to {} (which doesn’t override any of the default actual argument values used for validation).



34
35
36
37
38
39
40
 
# File 'lib/cascading/expr_stub.rb', line 34

def self.expr(expression, params = {})
  params = { :validate => true, :validate_with => {} }.merge(params)
  expr_stub = expression.kind_of?(ExprStub) ? expression : ExprStub.new(expression).compile
  expr_stub.validate(params[:validate_with]) if params[:validate]
  puts "Expression validation is disabled for '#{expression}'" unless params[:validate]
  expr_stub
end

Instance Method Details

#compile ⇒ Object

Scan, parse, and compile expression, then return this ExprStub upon success. Throws an CascadingException upon failure.



44
45
46
47
 
# File 'lib/cascading/expr_stub.rb', line 44

def compile
  evaluator
  self
end

#eval(actual_args) ⇒ Object

Evaluates this ExprStub given a hash mapping argument names to argument values. Names may be strings or symbols. Throws an CascadingException upon failure.



52
53
54
55
56
57
58
59
60
61
 
# File 'lib/cascading/expr_stub.rb', line 52

def eval(actual_args)
  actual_args = actual_args.inject({}) do |string_keys, (arg, value)|
    string_keys[arg.to_s] = specific_to_java(value, @types[arg.to_s])
    string_keys
  end
  args, values = split_hash(actual_args)
  unused = validate_fields(args)
  return self.eval(actual_args.reject{ |arg, value| unused.include?(arg) }) unless unused.empty?
  evaluate(values)
end

#to_s ⇒ Object 



24
25
26
 
# File 'lib/cascading/expr_stub.rb', line 24

def to_s
  @input_expression
end

#validate(actual_args = {}) ⇒ Object

Evaluates this ExprStub with default values for each actual argument. Values may be overridden with the optional actual_args argument, which accepts a hash like ExprStub#eval. Throws an CascadingException upon failure.



67
68
69
 
# File 'lib/cascading/expr_stub.rb', line 67

def validate(actual_args = {})
  self.eval(test_values.merge(actual_args))
end

#validate_fields(fields) ⇒ Object

Throws an exception if any arguments required by this ExprStub are missing from fields. Returns those fields which are unused. Throws an ExprArgException upon failure.

Raises:



78
79
80
81
82
83
 
# File 'lib/cascading/expr_stub.rb', line 78

def validate_fields(fields)
  names = @types.keys.sort
  missing = names - fields
  raise ExprArgException.new("Expression '#{@expression}' is missing these fields: #{missing.inspect}\nRequires: #{names.inspect}, found: #{fields.inspect}") unless missing.empty?
  fields - names
end

#validate_scope(scope) ⇒ Object 



71
72
73
 
# File 'lib/cascading/expr_stub.rb', line 71

def validate_scope(scope)
  validate_fields(scope.values_fields.to_a)
end