可以使用解构赋值来影响 CoffeeScript 中的投影吗?
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，它们似乎暗示在分配期间重命名对象可以用于投影(即映射、翻译、变换)源对象.
I'm having some trouble understanding destructuring assignment in CoffeeScript. The documentation contains a couple of examples which together seem to imply that renaming objects during assignment can be used to project (i.e. map, translate, transform) a source object.
我正在尝试将 a = [ { Id: 1, Name: 'Foo' }, { Id: 2, Name: 'Bar' } ] 投影到 b = [ {x: 1 }, { x: 2 } ].我尝试了以下但没有成功；我显然误解了一些东西.谁能解释这是否可能?
I am trying to project a = [ { Id: 1, Name: 'Foo' }, { Id: 2, Name: 'Bar' } ] into b = [ { x: 1 }, { x: 2 } ]. I've tried the following without success; I've clearly misunderstood something. Can anyone explain whether this is possible?
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
CoffeeScript 的并行赋值示例
theBait = 1000
theSwitch = 0
[theBait, theSwitch] = [theSwitch, theBait]
我将这个例子理解为暗示可以重命名变量，在这种情况下用于执行交换.
I understand this example as implying that variables can be renamed which in this case is used to perform a swap.
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
我将这个示例理解为从任意对象定义属性的选择，其中包括将数组的元素分配给变量.
I understand this example as defining a selection of properties from an arbitrary object which includes assigning the elements of an array to variables.
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
推荐答案
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>
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