将NSArray对象连接到一个字符串中,但需要能够指定属性

let array = ["Hello", "World", "!"]
let separator = ", "
let result = array.joined(separator: separator)
print(result) // 输出 "Hello, World, !"

let array = ["Hello", "World", "!"]
let separator = ", "
let result = array.map { $0.uppercased() }.joined(separator: separator)
print(result) // 输出 "HELLO, WORLD, !"