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?
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)"
}
}
}