我在理解CoffeeScript中的解构赋值时遇到了一些麻烦。 documentation包含几个示例,这些示例似乎一起暗示在赋值期间重命名对象可用于投影(即映射,转换,转换)源对象。
我正在尝试将a = [ { Id: 1, Name: 'Foo' }, { Id: 2, Name: 'Bar' } ]
投射到b = [ { x: 1 }, { x: 2 } ]
。我试过以下但没有成功;我明显误解了一些事情。任何人都可以解释这是否可能?
[ { x: 1 }, { x: 2 } ]
a = [ { Id: 1, Name: 'Foo' }, { Id: 2, Name: 'Bar' } ]
# Huh? This returns 1.
x = [ { Id } ] = a
# Boo! This returns [ { Id: 1, Name: 'Foo' }, { Id: 2, Name: 'Bar' } ]
y = [ { x: Id } ] = a
# Boo! This returns [ { Id: 1, Name: 'Foo' }, { Id: 2, Name: 'Bar' } ]
z = [ { Id: x } ] = a
theBait = 1000
theSwitch = 0
[theBait, theSwitch] = [theSwitch, theBait]
我理解这个例子暗示可以重命名变量,在这种情况下用于执行交换。
futurists =
sculptor: "Umberto Boccioni"
painter: "Vladimir Burliuk"
poet:
name: "F.T. Marinetti"
address: [
"Via Roma 42R"
"Bellagio, Italy 22021"
]
{poet: {name, address: [street, city]}} = futurists
我理解这个例子是从任意对象中定义一系列属性,包括将数组的元素分配给变量。
a = [
{ Id: 0, Name: { First: 'George', Last: 'Clinton' } },
{ Id: 1, Name: { First: 'Bill', Last: 'Bush' } },
]
# The old way I was doing it.
old_way = _.map a, x ->
{ Id: id, Name: { First: first, Last: last } } = x
{ id, first, last }
# Using thejh's solution...
new_way = ({id, first, last} for {Id: id, Name: {First: first, Last: last}} in a)
console.log new_way
答案 0 :(得分:3)
b = ({x} for {Id: x} in a)
有效:
coffee> a = [ { Id: 1, Name: 'Foo' }, { Id: 2, Name: 'Bar' } ]
[ { Id: 1, Name: 'Foo' },
{ Id: 2, Name: 'Bar' } ]
coffee> b = ({x} for {Id: x} in a)
[ { x: 1 }, { x: 2 } ]
coffee>
答案 1 :(得分:2)
CoffeeScript Cookbook解决与您完全相同的问题 - 解决方案是map:
b = a.map (hash) -> { x: hash.id }
c = ({ x: hash.id } for hash in a)
您可以查看this fiddle online on CoffeScript homepage(使用console.info显示结果)。
编辑:
要使其具有破坏性,只需将映射变量a
分配给自身:
a = a1 = [ { Id: 1, Name: 'Foo' }, { Id: 2, Name: 'Bar' } ]
a = a.map (hash) -> { x: hash.Id }
console.info a;
a1 = ({ x: hash.Id } for hash in a1)
console.info a1;