Ios 成员初始值设定项如何在结构中工作?(以Swift格式)
因为我是一个完全的初学者,我甚至不知道我问的问题是否正确。但是我很难理解为什么for循环中的“用户(名称:“John…”部分代码有效Ios 成员初始值设定项如何在结构中工作?(以Swift格式),ios,xcode,swift,cs193p,member-initialization,Ios,Xcode,Swift,Cs193p,Member Initialization,因为我是一个完全的初学者,我甚至不知道我问的问题是否正确。但是我很难理解为什么for循环中的“用户(名称:“John…”部分代码有效 CASE1 struct User { let name: String let company: String let login: String let password: String static let database: Dictionary<String, User> = { v
CASE1
struct User
{
let name: String
let company: String
let login: String
let password: String
static let database: Dictionary<String, User> = {
var theDatabase = Dictionary<String, User>()
for user in [
User(name: "John Appleseed", company: "Apple", login: "japple", password: "foo"),
User(name: "Madison Bumgarner", company: "World Champion San Francisco Giants", login: "madbum", password: "foo"),
User(name: "John Hennessy", company: "Stanford", login: "hennessy", password: "foo"),
User(name: "Bad Guy", company: "Criminals, Inc.", login: "baddie", password: "foo")
] {
theDatabase[user.login] = user
}
return theDatabase
}()
}
CASE1
struct User
{
let name: String
let company: String
let login: String
let password: String
static let database: Dictionary<String, User> = {
var theDatabase = Dictionary<String, User>()
for user in [
User(name: "John Appleseed", company: "Apple", login: "japple", password: "foo"),
User(name: "Madison Bumgarner", company: "World Champion San Francisco Giants", login: "madbum", password: "foo"),
User(name: "John Hennessy", company: "Stanford", login: "hennessy", password: "foo"),
User(name: "Bad Guy", company: "Criminals, Inc.", login: "baddie", password: "foo")
] {
theDatabase[user.login] = user
}
return theDatabase
}()
为了理解CASE1是如何工作的,我运行了一个更简单的代码版本,即CASE2。尽管在这两种情况下发生了完全相同的事情,[关于用户(…参数]),我在第二种情况下得到了错误“声明预期”。
Paul爵士(斯坦福cs193p)说这是一个相当简单的数据库,但我已经花了6个多小时试图解决这个问题。这非常简单。
CASE1
struct User
{
let name: String
let company: String
let login: String
let password: String
static let database: Dictionary<String, User> = {
var theDatabase = Dictionary<String, User>()
for user in [
User(name: "John Appleseed", company: "Apple", login: "japple", password: "foo"),
User(name: "Madison Bumgarner", company: "World Champion San Francisco Giants", login: "madbum", password: "foo"),
User(name: "John Hennessy", company: "Stanford", login: "hennessy", password: "foo"),
User(name: "Bad Guy", company: "Criminals, Inc.", login: "baddie", password: "foo")
] {
theDatabase[user.login] = user
}
return theDatabase
}()
[collection]中的使您能够对数组、字典或其他集合进行迭代。在案例1中,您可以创建用户数组:
CASE1
struct User
{
let name: String
let company: String
let login: String
let password: String
static let database: Dictionary<String, User> = {
var theDatabase = Dictionary<String, User>()
for user in [
User(name: "John Appleseed", company: "Apple", login: "japple", password: "foo"),
User(name: "Madison Bumgarner", company: "World Champion San Francisco Giants", login: "madbum", password: "foo"),
User(name: "John Hennessy", company: "Stanford", login: "hennessy", password: "foo"),
User(name: "Bad Guy", company: "Criminals, Inc.", login: "baddie", password: "foo")
] {
theDatabase[user.login] = user
}
return theDatabase
}()
[
User(), User()
]
但在第二种情况下,你没有。
此语法:[User(),User(),User()]创建数组。for循环必须包含在闭包中
CASE1
struct User
{
let name: String
let company: String
let login: String
let password: String
static let database: Dictionary<String, User> = {
var theDatabase = Dictionary<String, User>()
for user in [
User(name: "John Appleseed", company: "Apple", login: "japple", password: "foo"),
User(name: "Madison Bumgarner", company: "World Champion San Francisco Giants", login: "madbum", password: "foo"),
User(name: "John Hennessy", company: "Stanford", login: "hennessy", password: "foo"),
User(name: "Bad Guy", company: "Criminals, Inc.", login: "baddie", password: "foo")
] {
theDatabase[user.login] = user
}
return theDatabase
}()
在案例1中,您使用闭包声明一个名为database
的静态属性。以下是声明:
CASE1
struct User
{
let name: String
let company: String
let login: String
let password: String
static let database: Dictionary<String, User> = {
var theDatabase = Dictionary<String, User>()
for user in [
User(name: "John Appleseed", company: "Apple", login: "japple", password: "foo"),
User(name: "Madison Bumgarner", company: "World Champion San Francisco Giants", login: "madbum", password: "foo"),
User(name: "John Hennessy", company: "Stanford", login: "hennessy", password: "foo"),
User(name: "Bad Guy", company: "Criminals, Inc.", login: "baddie", password: "foo")
] {
theDatabase[user.login] = user
}
return theDatabase
}()
static let database: Dictionary<String, User> = {
// This is the body of the closure
}()
如您所见,我添加了数据库的声明和闭包,并在用户周围添加了[]
CASE1
struct User
{
let name: String
let company: String
let login: String
let password: String
static let database: Dictionary<String, User> = {
var theDatabase = Dictionary<String, User>()
for user in [
User(name: "John Appleseed", company: "Apple", login: "japple", password: "foo"),
User(name: "Madison Bumgarner", company: "World Champion San Francisco Giants", login: "madbum", password: "foo"),
User(name: "John Hennessy", company: "Stanford", login: "hennessy", password: "foo"),
User(name: "Bad Guy", company: "Criminals, Inc.", login: "baddie", password: "foo")
] {
theDatabase[user.login] = user
}
return theDatabase
}()