iphone - 实现 NSCopying

Question

我已阅读 NSCopying 文档，但我仍然不确定如何实现所需的内容。

我的类(class)供应商:

@interface Vendor : NSObject 
{
    NSString        *vendorID;
    NSMutableArray  *availableCars;
    BOOL            atAirport;
}

@property (nonatomic, copy) NSString *vendorID;
@property (nonatomic, retain) NSMutableArray *availableCars;
@property (nonatomic, assign) BOOL atAirport;

- (id)initFromVehVendorAvailsDictionary:(NSDictionary *)vehVendorAvails;

@end

Vendor 类有一个名为Car 的对象数组。

我的汽车对象:

@interface Car : NSObject 
{
    BOOL            isAvailable;
    NSString        *transmissionType;
    NSMutableArray  *vehicleCharges; 
    NSMutableArray  *fees; 
}

@property (nonatomic, assign) BOOL isAvailable;
@property (nonatomic, copy) NSString *transmissionType;
@property (nonatomic, retain) NSMutableArray *vehicleCharges;
@property (nonatomic, retain) NSMutableArray *fees;

- (id) initFromVehicleDictionary:(NSDictionary *)vehicleDictionary;

@end

因此，Vendor 拥有一个 Car 对象数组。 Car 包含 2 个其他自定义对象的数组。

Vendor 和 Car 都是从字典中初始化的。我将添加其中一种方法，它们可能相关也可能不相关。

-(id)initFromVehVendorAvailsDictionary:(NSDictionary *)vehVendorAvails {

    self.vendorCode      = [[vehVendorAvails objectForKey:@"Vendor"] 
                           objectForKey:@"@Code"];

    self.vendorName      = [[vehVendorAvails objectForKey:@"Vendor"] 
                           objectForKey:@"@CompanyShortName"];

    self.vendorDivision  = [[vehVendorAvails objectForKey:@"Vendor"]   
                           objectForKey:@"@Division"];

    self.locationCode    = [[[vehVendorAvails objectForKey:@"Info"] 
                           objectForKey:@"LocationDetails"] 
                           objectForKey:@"@Code"];

    self.atAirport       = [[[[vehVendorAvails objectForKey:@"Info"] 
                           objectForKey:@"LocationDetails"] 
                           objectForKey:@"@AtAirport"] boolValue];

    self.venLocationName = [[[vehVendorAvails objectForKey:@"Info"] 
                           objectForKey:@"LocationDetails"] 
                           objectForKey:@"@Name"];

    self.venAddress      = [[[[vehVendorAvails objectForKey:@"Info"] 
                           objectForKey:@"LocationDetails"] 
                           objectForKey:@"Address"] 
                           objectForKey:@"AddressLine"];

    self.venCountryCode  = [[[[[vehVendorAvails objectForKey:@"Info"]  
                           objectForKey:@"LocationDetails"] 
                           objectForKey:@"Address"] 
                           objectForKey:@"CountryName"]
                           objectForKey:@"@Code"];

    self.venPhone        = [[[[vehVendorAvails objectForKey:@"Info"]  
                           objectForKey:@"LocationDetails"]        
                           objectForKey:@"Telephone"] 
                           objectForKey:@"@PhoneNumber"];

    availableCars        = [[NSMutableArray alloc] init];

    NSMutableArray *cars = (NSMutableArray *)[vehVendorAvails objectForKey:@"VehAvails"];

    for (int i = 0; i < [cars count]; i++) {

        Car *car = [[Car alloc] initFromVehicleDictionary:[cars objectAtIndex:i]];
        [availableCars addObject:car];
        [car release];
    }

    self.venLogo = [[[vehVendorAvails objectForKey:@"Info"] 
                   objectForKey:@"TPA_Extensions"] 
                   objectForKey:@"VendorPictureURL"];

    return self;
}

所以总结一下这个可怕的问题。

我需要复制一组 Vendor 对象。我相信我需要在 Vendor 上实现 NSCopying 协议(protocol)，这可能意味着我也需要在 Car 上实现它，因为 Vendor 包含 Car 的数组。这意味着我还需要在属于 Car 对象的 2 个数组中保存的类上实现它。

如果我能得到一些关于在 Vendor 上实现 NSCopying 协议(protocol)的指导，我将不胜感激，我在任何地方都找不到这方面的任何教程。

Answer 1

实现NSCopying ，您的对象必须响应 -copyWithZone: 选择器。以下是您声明遵守它的方式:

@interface MyObject : NSObject <NSCopying> {

然后，在你的对象的实现中(你的 .m 文件):

- (id)copyWithZone:(NSZone *)zone
{
    // Copying code here.
}

您的代码应该做什么？首先，创建对象的一个​​新实例——您可以调用 [[[self class] alloc] init] 来获取当前类的初始化对象，这对于子类化很有效。然后，对于任何支持复制的 NSObject 子类的实例变量，您可以为新对象调用 [thatObject copyWithZone:zone]。对于原始类型(int、char、BOOL 和 friend )，只需将变量设置为相等即可。因此，对于您的对象供应商，它看起来像这样:

- (id)copyWithZone:(NSZone *)zone
{
    id copy = [[[self class] alloc] init];

    if (copy) {
        // Copy NSObject subclasses
        [copy setVendorID:[[self.vendorID copyWithZone:zone] autorelease]];
        [copy setAvailableCars:[[self.availableCars copyWithZone:zone] autorelease]];

        // Set primitives
        [copy setAtAirport:self.atAirport];
    }

    return copy;
}