kotlin - "with"在 Kotlin 中是什么意思？

Question

我已经阅读了 3 次关于它的文档，但我仍然不知道它的作用。有人可以 ELI5(像我五岁一样解释)吗？以下是我的使用方法:

fun main(args: Array<String>) {
    val UserModel = UserModel()
    val app = Javalin.create().port(7000).start()

    with (app) {
        get("/users") {
            context -> context.json(UserModel)
        }
    }
}

Answer 1

with 用于访问对象的成员和方法，而不必每次访问都引用该对象。它(主要)用于缩写您的代码。在构造对象的时候经常用到:

// Verbose way, 204 characters:
var thing = Thingummy()
thing.component1 = something()
thing.component2 = somethingElse()
thing.component3 = constantValue
thing.component4 = foo()
thing.component5 = bar()
parent.children.add(thing)
thing.refcount = 1

// Terse way, 182 characters:
var thing = Thingummy()
with(thing) {
  component1 = something()
  component2 = somethingElse()
  component3 = constantValue
  component4 = foo()
  component5 = bar()
  parent.children.add(this)
  refcount = 1
}