Class | Ruote::Exp::IncExpression |
In: |
lib/ruote/exp/fe_inc.rb
|
Parent: | SequenceExpression |
Increments or decrements the value found in a process variable or a workitem field.
One points to a var or a field in these various ways :
sequence do inc :var => 'counter' inc :field => 'counter' inc 'v:counter' inc 'f:counter' end
‘inc’ and ‘dec’ work with two types of values : numbers (the default) and arrays.
The vanilla case of inc/dec is increasing/decreasing a value by 1.
dec :var => 'x'
will decrease the value in variable ‘x’ by 1.
inc/dec works with two kind of numbers, integers and floats.
If the target var or field is not set, it will be assumed to be at zero.
The default increment is 1 (or 1.0 for floats). It can be changed by passing a value to the inc/dec expression.
inc 'v:x', :val => 3 inc 'v:y', :val => 2.4
inc/dec can be used to push/pop elements in arrays held in process variables or workitem fields.
This fragment of process definition
sequence do set 'v:x' => %w[ a b c d ] repeat do dec 'v:x', :pos => 'head' _break :unless => '${__result__}' participant '${__result__}' end end
is equivalent to
iterator :on => 'a, b, c, d', :to_var => 'x' do participant '${v:x}' end
More details : the inc expression expects a value and it will place it at the end of the current array. The :pos or :position attribute can be set to ‘head’ to let the inc expression place the value at the head of the array.
set 'v:x' => [ 'alfred', 'bryan' ] set 'v:customer_name' => 'charles' inc 'v:x', :val => '${v:customer_name}' # the variable 'x' now holds [ 'alfred', 'bryan', 'charles' ] inc 'v:y', :val => '${v:customer_name}', :pos => 'head' # the variable 'x' now holds [ 'charles', 'alfred', 'bryan', 'charles' ]
The ‘dec’ / ‘decrement’ variant of the expression will remove the tail value (by default) of the array, or the head value if :pos is set to ‘head’.
It‘s also possible to remove a specific value by passing it to ‘dec’ :
set 'v:x' => [ 'alfred', 'bryan', 'carl' ] dec 'v:x', :val => 'bryan' # the variable 'x' now holds [ 'alfred', 'carl' ]
‘dec’ places the removed value in workitem field ‘result’. This trick was used in the above iterator example.
A specific variable or field can be specified via the :to_var / :to_field attributes :
dec 'v:x', :to_v => 'a' participant :ref => '${v:a}'
(Since ruote 2.3.0)
If nested expressions are provided the result workitem field is used for inc.
inc 'v:x' do set '__result__' => 3 end
will increase the value of the variable x by 3.
push and pop are aliases for inc and dec respectively. There is a major difference though: they‘ll force the target value into an array.
sequence do set 'v:x' => 2 push 'v:x' => 3 end
will result in a variable x holding [ 2, 3 ] as value.
Likewise,
pop 'v:x'
will force a value of [] into the variable x if it wasn‘t previously set or its value was not an array with more than one element.