Question

我对如何“设置”和“获取”另一个包含的对象的实例变量感到有些困惑。从下面的代码中可以看出，我首先创建一个包含SolidRocketMotor对象的RocketBody。我在RocketBody init中创建SolidRocketMotor并在RocketBody dealloc中释放它。

我的问题是如何在main（例如设置engCase）中设置/获取引擎（SolidRocketMotor）实例变量？

int main (int argc, const char * argv[]) {
    RocketBody *ares_1x;

    ares_1x = [[RocketBody alloc] init];
    [ares_1x setFuel: [NSNumber numberWithInt:50000]];
    [ares_1x setWeight:[NSNumber numberWithFloat:1.8]];
    // How to set engCase to "Standard" here?
...

@interface SolidRocketMotor : NSObject
{
    NSString *engCase;        
    NSString *engPropellant;  
    NSNumber *engIgniter;    
    NSString *engNozzle;      
}
@property(copy) NSString *engCase;
@property(copy) NSString *engPropellant;
@property(copy) NSNumber *engIgniter;
@property(copy) NSString *engNozzle;
@end

@interface RocketBody : NSObject
{
    NSNumber *fuel;
    NSNumber *weight;
    BOOL holdDownBolt_01;
    BOOL holdDownBolt_02;
    BOOL holdDownBolt_03;
    BOOL holdDownBolt_04;
    SolidRocketMotor *engine;
}
@property(copy) NSNumber *fuel;
@property(copy) NSNumber *weight;
@property BOOL holdDownBolt_01;
@property BOOL holdDownBolt_02;
@property BOOL holdDownBolt_03;
@property BOOL holdDownBolt_04;
@end

// ------------------------------------------------------------------- **
// IMPLEMENTATION
// ------------------------------------------------------------------- **

@implementation SolidRocketMotor
- (id) init {
    self = [super init];
    if (self) NSLog(@"_init: %@", NSStringFromClass([self class]));
    return self;
}

@synthesize engCase;
@synthesize engPropellant;
@synthesize engIgniter;
@synthesize engNozzle;

- (void) dealloc {
    NSLog(@"_deal: %@", NSStringFromClass([self class]));
    [super dealloc];
}
@end

// ------------------------------------------------------------------- **

@implementation RocketBody
- (id) init {
    self = [super init];
    if (self) {
        engine = [[SolidRocketMotor alloc] init];
        NSLog(@"_init: %@", NSStringFromClass([self class]));
    }
    return self;
}

@synthesize fuel;
@synthesize weight;
@synthesize holdDownBolt_01;
@synthesize holdDownBolt_02;
@synthesize holdDownBolt_03;
@synthesize holdDownBolt_04;

- (void) dealloc {
    NSLog(@"_deal: %@", NSStringFromClass([self class]));
    [engine release], engine = nil;
    [super dealloc];
}
@end

非常感谢

加里

Answer 1

假设您有类似的东西并且您声明了SolidRocketMotor *引擎的属性设置：

RocketBody *rb = [[RocketBody alloc] init];

然后你会这样做：

SolidRocketMotor *srm = [[SolidRocketMotor alloc] init];

rb.engine = srm;

和

rb.engine.engCase = whatever;

Answer 2

您需要在engine课程中为RocketBody提供一个访问者。像这样：

@interface RocketBody : NSObject
{
    // ...
    SolidRocketMotor *engine;
}
// ...
@property(retain) SolidRocketMotor *engine;
@end

@implementation RocketBody
// ...
@synthesize engine;
// ...
@end

有了这个，外部代码可以访问engine属性：

// Obj-C 2.0 Property style:
ares_1x.engine.engCase = @"Standard";

// or setter/getter method style:
[[ares_1x engine] setEngCase:@"Standard"];

访问对象中的对象？

2 个答案: