Swift结构体返回零问题

Question

我有这个结构，如果我运行这个代码，我会得到nil。我在另一个结构中使用了一个结构。接下来，我设置了第一个变量，并将值放入另一个变量中。参见下面的代码

struct Main: codable{
let name: String?
let url: [SiteUrl]?
}
struct SiteUrl: codable{
let url: String?
}
struct People: codable{
let nickname: string?
let url: [SiteUrl]
}
var test :Main?
test.url.append(“test”)
var people: People?
people?.url = test.url
print(test)//result nil

Answer 1

这是因为

var test: Main?是可选

在分配之前，您需要先实例化测试。

所以答案是

var test :Main?
var name: String = "name"
var url: [SiteUrl] = []
test = Main(name: name,  url )
test.url.append(“test”)
var people: People?
people?.url = test.url
print(test)//result nil

或者，你可以只做下面更简单的

var test : Main? = Main(name: "name", [])
test.url.append(“test”)
var people: People?
people?.url = test.url
print(test)//result nil