2, closing bag
(1 Overview
l Closure is a powerful method for transmitting executing code blocks.
l You can view the closure as anonymous in Java, but only a single (anonymous) method.
l Hethers can be used as an alternative to circulation
[1, 2, 3, 4]. Each {Println (IT)}
l Use closures to make exception handling and closing resources easier, for example, please see Groovy SQL
(2) Compare closure and anonymous inside categories
l Different from Java anonymous inside, Groovy supports "True Closure": The status can be passed to the outside of the closure
l Partial variables can be used and modified when closing, and any variable created in the closure can be used as partial variables, visible to the outside.
l Look at the example below:
COUNT = 0
Last = 0
[1, 2, 3, 4] .each {count = it; las = it}
Println ("The Sum IS $ {Count} and the last item was $ {last}")
Output Result: The Sum is 10 and the last item was 4
(3) Closed bag is a normal object
l Closure is the object that is passed and called when needed.
l can therefore be used as it is as follows:
C = {Println ("Hello $ {IT}")}
C.call ('James')
c.call ('bob ")
l Closets are compiled into new classes for expanding the Groovy.lang.Closure class.
l The following omitted Writings is equivalent.
C = {Println ("Hello $ {IT}")}
C ('James')
C ('bob')
(4) Parameters of closed bags
l Closure can have any number of parameters
l Default, closed bag has a single default parameter: "IT"
l You can specify a list of parameters in the beginning of the closure statement.
C = {A, B, C | Println ("Hello $ {a} $ {b} $ {c}")}
C ('Cheese', 234, 'Gromit')
l The following is another useful example of using two parameters, and it has been told in "Groovy Quick Start":
Value = [1, 2, 3] .inject ('counting:') {STR, ITEM | STR ITEM}
askERT VALUE == "Counting: 123"
Value = [1, 2, 3] .INJECT (0) {count, item | count item}
askERT VALUE == 6
