xcode - 左移 (<<) 在 Swift 中实际上做了什么？

Question

我正在摆弄一个 Flappy Bird 的克隆，我无法弄清楚以下代码的含义

let birdCategory: UInt32 = 1 << 0
let worldCategory: UInt32 = 1 << 1
let pipeCategory: UInt32 = 1 << 2
let scoreCategory: UInt32 = 1 << 3

抱歉，如果这很明显，我已经尝试寻找答案但找不到。谢谢

Answer 1

这就是按位左移运算符

基本上就是这样

// moves 0 bits to left for 00000001
let birdCategory: UInt32 = 1 << 0 

// moves 1 bits to left for 00000001 then you have 00000010 
let worldCategory: UInt32 = 1 << 1

// moves 2 bits to left for 00000001 then you have 00000100 
let pipeCategory: UInt32 = 1 << 2

// moves 3 bits to left for 00000001 then you have 00001000 
let scoreCategory: UInt32 = 1 << 3

你最终拥有

birdCategory = 1
worldCategory = 2
pipeCategory = 4
scoreCategory= 8