NSURLComponents如何用于解析和构建复杂的URL

NSURLComponents类可以用于解析和构建复杂的URL。它提供了一种方便的方式来访问URL的各个部分，如协议、主机、路径、查询参数和片段。下面是一个使用NSURLComponents解析和构建URL的示例：

1. 解析URL:

let urlString = "https://www.example.com/path/to/resource?param1=value1&param2=value2#fragment"
if let url = URL(string: urlString), let components = URLComponents(url: url, resolvingAgainstBaseURL: false) {
    print(components.scheme) // "https"
    print(components.host) // "www.example.com"
    print(components.path) // "/path/to/resource"
    
    if let queryItems = components.queryItems {
        for item in queryItems {
            print("\(item.name)=\(item.value ?? "")") // "param1=value1", "param2=value2"
        }
    }
    
    if let fragment = components.fragment {
        print(fragment) // "fragment"
    }
}

2. 构建URL:

var components = URLComponents()
components.scheme = "https"
components.host = "www.example.com"
components.path = "/path/to/resource"
components.queryItems = [
    URLQueryItem(name: "param1", value: "value1"),
    URLQueryItem(name: "param2", value: "value2")
]
components.fragment = "fragment"

if let url = components.url {
    print(url.absoluteString) // "https://www.example.com/path/to/resource?param1=value1&param2=value2#fragment"
}

通过使用NSURLComponents类，可以轻松地解析和构建复杂的URL，使得处理URL更加方便和灵活。