Swift中的惰性属性初始化

概述你如何在Swift中实现以下模式？ Container类使用包含字典的JSON数组进行初始化.这些词典用于初始化Entry类.但是,当访问条目或searchEntries属性时,Entry对象的初始化会延迟发生. @interface Container@property (readonly, nonatomic) NSArray *entryDicts;@property (readon 你如何在Swift中实现以下模式？

Container类使用包含字典的JsON数组进行初始化.这些词典用于初始化Entry类.但是,当访问条目或searchEntrIEs属性时,Entry对象的初始化会延迟发生.

@interface Container@property (Readonly,nonatomic) NSArray *entryDicts;@property (Readonly,nonatomic) NSArray* entrIEs;@property (Readonly,nonatomic) NSDictionary *searchEntrIEs;@end@implementation Container- (instancetype)initWithArray:(NSArray *)array{    self = [super init];    if (self) {        _entryDicts = array;    }    return self;}@synthesize entrIEs = _entrIEs;- (NSArray *)entrIEs{    [self loadEntrIEsIfNeeded];    return _entrIEs;}@synthesize entrIEsByNumber = _entrIEsByNumber;- (NSDictionary *)entrIEsByNumber{    [self loadEntrIEsIfNeeded];    return _entrIEsByNumber;}- (voID)loadEntrIEsIfNeeded{    if (_entrIEs == nil) {        // Load entrIEs        NSMutableArray *entrIEs = [NSMutableArray arrayWithCapacity:[self.entrIEsDict count]];        NSMutableDictionary *entrIEsByNumber = [NSMutableDictionary dictionaryWithCapacity:[self.entrIEsDict count]];        [self.entrIEsDict enumerateKeysAndobjectsUsingBlock:^(Nsstring *number,NSDictionary *entryDict,BOol *stop) {            Entry *entry = [[Entry alloc] initWithDictionary:entryDict container:self];            [entrIEs addobject:entry];            entrIEsByNumber[number] = entry;        }];        _entrIEs = [entrIEs copy];        _entrIEsByNumber = [entrIEsByNumber copy];        // Delete dictionarIEs        _entrIEsDict = nil;    }}@end

似乎这个问题已基本得到回答,但要回到原帖,这里(恕我直言)是一个相对简洁的Swift翻译.关键是你可以链接惰性属性.请注意,我同时使用了类函数和闭包 – 两者都很好.

import Swiftprintln("begin")class ClassWithLazyPropertIEs {    lazy var entrIEs:[String] = ClassWithLazyPropertIEs.loadStuff()    lazy var entrIEsByNumber:Dictionary<Int,String> = {        var d = Dictionary<Int,String>()        for i in 0..<self.entrIEs.count {            d[i] = self.entrIEs[i]        }        return d    }()    private class func loadStuff() -> [String] {        return ["Acai","Apples","Apricots","Avocado","Ackee","Bananas","BilberrIEs"]    }}let c = ClassWithLazyPropertIEs()c.entrIEsByNumber    // 0: "Acai",1: "Apples",2: "Apricots",3: "Avocado",4: "Ackee",5: "Bananas",6: "BilberrIEs"]println("end")

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