2月 8, 2022 | Nix.Huang

closure

//通过方法引用获取闭包
Closure smallerSix = six.&filter

this:enclosing class where the closure is defined
owner:enclosing class or enclosing closure where the closure is defined
delegate: default to owner

class Person { String name def pretty = { "My name is $name" } } def p = new Person(name: 'Sarah') def t = new Thing(name: 'Teapot') p.pretty.resolveStrategy = Closure.DELEGATE_FIRST; //default OWNER_FIRST p.pretty.delegate = t assert p.toString() == 'My name is Teapot'

1
2
3
4
5
6
7
8
9
10

class Person {
    String name
    def pretty = { "My name is $name" }
}
def p = new Person(name: 'Sarah')
def t = new Thing(name: 'Teapot')
p.pretty.resolveStrategy = Closure.DELEGATE_FIRST; //default OWNER_FIRST
p.pretty.delegate = t
assert p.toString() == 'My name is Teapot'

闭包的两种使用方式

def adder = { x, y -> return x+y }
assert adder(4, 3) == 7 
assert adder.call(2, 6) == 8

def adder = { x, y -> return x+y }

assert adder(4, 3) == 7

assert adder.call(2, 6) == 8

//如果参数是闭包，可以将其放在括号后
//int.times应该是groovy的扩展方法
def benchmark(int repeat, Closure worker) {
repeat.times { worker(it) } 
}

//如果参数是闭包，可以将其放在括号后

//int.times应该是groovy的扩展方法

def benchmark(int repeat, Closure worker) {

repeat.times { worker(it) }

}

curry从左向右固定参数，成为另一个闭包

def adder = { x, y -> return x+y } 
def addOne = adder.curry(1) 
assert addOne(5) == 6

def adder = { x, y -> return x+y }

def addOne = adder.curry(1)

assert addOne(5) == 6

range

def range = left..<right;
range.contains 4;
//previous next 用于++ 操作符，
//实现Comparable 接口实现<=>操作符

def range = left..<right;

range.contains 4;

//previous next 用于++ 操作符，

//实现Comparable 接口实现<=>操作符

*将将集合中元素插入到另一个集合

//list * spread operator
List myList = [1, 2, 3]
List flat = [0, *myList, 4]
//*myList 表示将元素插入flat ，而不是mylist本身
//getAt，putAt 用于支持下标操作

//list * spread operator

List myList = [1, 2, 3]

List flat = [0, *myList, 4]

//*myList 表示将元素插入flat ，而不是mylist本身

//getAt，putAt 用于支持下标操作

map

//map
def myMap = [a:1, b:2, c:3]
def emptyMap = [:]
def composed = [x:'y', *:myMap]
//retrieve
myMap.a  myMap['a'] myMap.get('a')

//map

def myMap = [a:1, b:2, c:3]

def emptyMap = [:]

def composed = [x:'y', *:myMap]

//retrieve

myMap.a myMap['a'] myMap.get('a')

simple datatypes

1.23 //default bigDecimal 
[1, 2, 3].collect { it * 2 }
//safe navigation operator
if(company.getContact()?.getAddress()?.getCountry() == Country.NEW_ZEALAND) { ... }
//default value
def name = client.getName() ?: ""

1.23 //default bigDecimal

[1, 2, 3].collect { it * 2 }

//safe navigation operator

if(company.getContact()?.getAddress()?.getCountry() == Country.NEW_ZEALAND) { ... }

//default value

def name = client.getName() ?: ""

Posted in: IT人生

知行合一，止于至善

groovy cheat list

closure

站内搜索