我在玩苹果的新Swift编程语言，遇到了一些问题…
目前我试图读取一个plist文件，在Objective-C中，我会做以下工作来获取内容作为NSDictionary:
NSString *filePath = [[NSBundle mainBundle] pathForResource:@"Config" ofType:@"plist"];
NSDictionary *dict = [[NSDictionary alloc] initWithContentsOfFile:filePath];
我如何得到一个plist作为一个字典在Swift?
我假设我可以得到路径到plist:
let path = NSBundle.mainBundle().pathForResource("Config", ofType: "plist")
当这工作(如果它是正确的?):我如何获得内容作为一个字典?
还有一个更普遍的问题:
是否可以使用默认的NS*类?我想是的……还是我遗漏了什么?据我所知，默认框架NS*类仍然有效，可以使用吗?
当前回答
你仍然可以在Swift中使用nsdictionary:
Swift 4
var nsDictionary: NSDictionary?
if let path = Bundle.main.path(forResource: "Config", ofType: "plist") {
nsDictionary = NSDictionary(contentsOfFile: path)
}
Swift 3+
if let path = Bundle.main.path(forResource: "Config", ofType: "plist"),
let myDict = NSDictionary(contentsOfFile: path){
// Use your myDict here
}
以及旧版本的Swift
var myDict: NSDictionary?
if let path = NSBundle.mainBundle().pathForResource("Config", ofType: "plist") {
myDict = NSDictionary(contentsOfFile: path)
}
if let dict = myDict {
// Use your dict here
}
NSClasses仍然可用，完全可以在Swift中使用。我想他们可能很快就会把重点转移到swift上，但是目前swift api并没有核心NSClasses的所有功能。
其他回答
Plist是一个简单的Swift枚举，用于处理属性列表。
// load an applications info.plist data
let info = Plist(NSBundle.mainBundle().infoDictionary)
let identifier = info["CFBundleIndentifier"].string!
更多的例子:
import Plist
// initialize using an NSDictionary
// and retrieve keyed values
let info = Plist(dict)
let name = info["name"].string ?? ""
let age = info["age"].int ?? 0
// initialize using an NSArray
// and retrieve indexed values
let info = Plist(array)
let itemAtIndex0 = info[0].value
// utility initiaizer to load a plist file at specified path
let info = Plist(path: "path_to_plist_file")
// we support index chaining - you can get to a dictionary from an array via
// a dictionary and so on
// don't worry, the following will not fail with errors in case
// the index path is invalid
if let complicatedAccessOfSomeStringValueOfInterest = info["dictKey"][10]["anotherKey"].string {
// do something
}
else {
// data cannot be indexed
}
// you can also re-use parts of a plist data structure
let info = Plist(...)
let firstSection = info["Sections"][0]["SectionData"]
let sectionKey = firstSection["key"].string!
let sectionSecret = firstSection["secret"].int!
Plist.swift
Plist本身非常简单，下面是它的清单，以防你直接引用。
//
// Plist.swift
//
import Foundation
public enum Plist {
case dictionary(NSDictionary)
case Array(NSArray)
case Value(Any)
case none
public init(_ dict: NSDictionary) {
self = .dictionary(dict)
}
public init(_ array: NSArray) {
self = .Array(array)
}
public init(_ value: Any?) {
self = Plist.wrap(value)
}
}
// MARK:- initialize from a path
extension Plist {
public init(path: String) {
if let dict = NSDictionary(contentsOfFile: path) {
self = .dictionary(dict)
}
else if let array = NSArray(contentsOfFile: path) {
self = .Array(array)
}
else {
self = .none
}
}
}
// MARK:- private helpers
extension Plist {
/// wraps a given object to a Plist
fileprivate static func wrap(_ object: Any?) -> Plist {
if let dict = object as? NSDictionary {
return .dictionary(dict)
}
if let array = object as? NSArray {
return .Array(array)
}
if let value = object {
return .Value(value)
}
return .none
}
/// tries to cast to an optional T
fileprivate func cast<T>() -> T? {
switch self {
case let .Value(value):
return value as? T
default:
return nil
}
}
}
// MARK:- subscripting
extension Plist {
/// index a dictionary
public subscript(key: String) -> Plist {
switch self {
case let .dictionary(dict):
let v = dict.object(forKey: key)
return Plist.wrap(v)
default:
return .none
}
}
/// index an array
public subscript(index: Int) -> Plist {
switch self {
case let .Array(array):
if index >= 0 && index < array.count {
return Plist.wrap(array[index])
}
return .none
default:
return .none
}
}
}
// MARK:- Value extraction
extension Plist {
public var string: String? { return cast() }
public var int: Int? { return cast() }
public var double: Double? { return cast() }
public var float: Float? { return cast() }
public var date: Date? { return cast() }
public var data: Data? { return cast() }
public var number: NSNumber? { return cast() }
public var bool: Bool? { return cast() }
// unwraps and returns the underlying value
public var value: Any? {
switch self {
case let .Value(value):
return value
case let .dictionary(dict):
return dict
case let .Array(array):
return array
case .none:
return nil
}
}
// returns the underlying array
public var array: NSArray? {
switch self {
case let .Array(array):
return array
default:
return nil
}
}
// returns the underlying dictionary
public var dict: NSDictionary? {
switch self {
case let .dictionary(dict):
return dict
default:
return nil
}
}
}
// MARK:- CustomStringConvertible
extension Plist : CustomStringConvertible {
public var description:String {
switch self {
case let .Array(array): return "(array \(array))"
case let .dictionary(dict): return "(dict \(dict))"
case let .Value(value): return "(value \(value))"
case .none: return "(none)"
}
}
}
斯威夫特4.0
现在可以使用decodedable协议将.plist解码为自定义结构。我将介绍一个基本的例子，对于更复杂的。plist结构，我建议阅读Decodable/Encodable(一个很好的资源是:https://benscheirman.com/2017/06/swift-json/)。
首先将结构设置为.plist文件的格式。对于这个例子，我将考虑一个根级字典和3个条目:1个字符串键“name”，1个Int键“age”，1个布尔键“single”。下面是结构体:
struct Config: Decodable {
private enum CodingKeys: String, CodingKey {
case name, age, single
}
let name: String
let age: Int
let single: Bool
}
很简单。现在是最酷的部分。使用PropertyListDecoder类，我们可以很容易地将.plist文件解析为这个结构体的实例化:
func parseConfig() -> Config {
let url = Bundle.main.url(forResource: "Config", withExtension: "plist")!
let data = try! Data(contentsOf: url)
let decoder = PropertyListDecoder()
return try! decoder.decode(Config.self, from: data)
}
不用担心太多代码，而且都在Swift中。更好的是，我们现在有一个Config结构的实例化，我们可以很容易地使用:
let config = parseConfig()
print(config.name)
print(config.age)
print(config.single)
打印。plist中“name”、“age”和“single”键的值。
能在一行内完成吗
var dict = NSDictionary(contentsOfFile: NSBundle.mainBundle().pathForResource("Config", ofType: "plist"))
你可以使用它，我在github https://github.com/DaRkD0G/LoadExtension中创建了一个简单的字典扩展
extension Dictionary {
/**
Load a Plist file from the app bundle into a new dictionary
:param: File name
:return: Dictionary<String, AnyObject>?
*/
static func loadPlistFromProject(filename: String) -> Dictionary<String, AnyObject>? {
if let path = NSBundle.mainBundle().pathForResource("GameParam", ofType: "plist") {
return NSDictionary(contentsOfFile: path) as? Dictionary<String, AnyObject>
}
println("Could not find file: \(filename)")
return nil
}
}
你可以用它来计算负载
/**
Example function for load Files Plist
:param: Name File Plist
*/
func loadPlist(filename: String) -> ExampleClass? {
if let dictionary = Dictionary<String, AnyObject>.loadPlistFromProject(filename) {
let stringValue = (dictionary["name"] as NSString)
let intergerValue = (dictionary["score"] as NSString).integerValue
let doubleValue = (dictionary["transition"] as NSString).doubleValue
return ExampleClass(stringValue: stringValue, intergerValue: intergerValue, doubleValue: doubleValue)
}
return nil
}
你仍然可以在Swift中使用nsdictionary:
Swift 4
var nsDictionary: NSDictionary?
if let path = Bundle.main.path(forResource: "Config", ofType: "plist") {
nsDictionary = NSDictionary(contentsOfFile: path)
}
Swift 3+
if let path = Bundle.main.path(forResource: "Config", ofType: "plist"),
let myDict = NSDictionary(contentsOfFile: path){
// Use your myDict here
}
以及旧版本的Swift
var myDict: NSDictionary?
if let path = NSBundle.mainBundle().pathForResource("Config", ofType: "plist") {
myDict = NSDictionary(contentsOfFile: path)
}
if let dict = myDict {
// Use your dict here
}
NSClasses仍然可用，完全可以在Swift中使用。我想他们可能很快就会把重点转移到swift上，但是目前swift api并没有核心NSClasses的所有功能。
