題目一
var car = "大奔"
let block = { (car: String) in
print("我開\(car)")
}
car = "雅迪"
block(car)
block的參數(shù)是外界傳入的，調(diào)用時(shí)block傳入的參數(shù)值為"雅迪"，所以答案為
我開雅迪
題目二
var car = "大奔"
let block = { [ car ] in
print("我開\(car)")
}
car = "雅迪"
block()
block在調(diào)用之前耘擂，將car捕獲為自身局部變量，捕獲時(shí)car的值為"大奔"絮姆，所以答案為
我開大奔
題目三
var car = "大奔"
let block = {
print("我開\(car)")
}
car = "雅迪"
block()
block沒有對(duì)car進(jìn)行復(fù)制醉冤，所以block內(nèi)部的car還是全局的car變量，所以答案為
我開雅迪
題目四
class Car {
var name: String = ""
}
var car = Car()
car.name = "大奔"
let block = { [ car ] in
print("我開\(car?.name)")
}
car.name = "雅迪"
block()
block在調(diào)用之前篙悯，將car捕獲為自身的局部變量蚁阳，但是car的name屬性為指針類型，所以答案為
我開雅迪
題目五
在題目四的基礎(chǔ)上鸽照，在name重新賦值前螺捐，更新car的指針指向，即
class Car {
var name: String = ""
}
var car = Car()
car.name = "大奔"
let block = { [ car ] in
print("我開\(car.name)")
}
car = Car()
car.name = "雅迪"
block()
block在調(diào)用之前，將car捕獲為自身的局部變量定血，又因?yàn)閏ar在block調(diào)用之前就被重新賦值赔癌，所以block捕獲的car與外界的car不是同一個(gè)，block捕獲的car還是car在第二次賦值前的那個(gè)澜沟，即name="大奔"届榄。所以答案為
我開大奔
題目六
在題目五的基礎(chǔ)上，捕獲的car用weak修飾倔喂，即
class Car {
var name: String = ""
}
var car = Car()
car.name = "大奔"
let block = { [ weak car ] in
print("我開\(car?.name)")
}
car = Car()
car.name = "雅迪"
block()
如題五的解釋的基礎(chǔ)上铝条，因?yàn)椴东@的car為弱引用類型，所以此時(shí)car在block中相當(dāng)于做了一次淺拷貝席噩，在car被重新賦值時(shí)班缰，原指針被銷毀。所以答案為
我開nil
