Question

这是我的第一个自定义类'实现

第一个标题

#import <Foundation/Foundation.h>

@interface BNRStockHolding : NSObject

@property (nonatomic) float purchaseSharePrice;
@property (nonatomic) float currentSharePrice;
@property (nonatomic) int numberOfShares;
-(float)costInDollars;
-(float)valueInDollars;

@end

首次实施

#import "BNRStockHolding.h"

@implementation BNRStockHolding

-(float)costInDollars{
    float cost = [self purchaseSharePrice]*[self numberOfShares];
    return cost;
}

-(float)valueInDollars{
    float value = [self currentSharePrice]*[self numberOfShares];
    return value;
}

@end

子类标题＃进口 #import“BNRStockHolding.h”

@interface BNRForeignStockHolding : BNRStockHolding

@property (nonatomic) float converstionRate;

@end

这是子类'implementation

#import "BNRForeignStockHolding.h"

@implementation BNRForeignStockHolding

-(float)costInDollars{
    float normalCost = [super costInDollars];
    return normalCost*[self converstionRate];
}

-(float)valueInDollars{
    float normalValue = [super valueInDollars];
    return normalValue*[self converstionRate];
}

@end

主

#import <Foundation/Foundation.h>
#import "BNRForeignStockHolding.h"


int main

(int argc, const char * argv[])

{

    @autoreleasepool {

        BNRStockHolding *AAPL = [[BNRStockHolding alloc]init];
        BNRStockHolding *GOOG = [[BNRStockHolding alloc]init];
        BNRStockHolding *NYSE = [[BNRStockHolding alloc]init];

        NSMutableArray *stockArray = [NSMutableArray array];

        AAPL.purchaseSharePrice=2.30;
        AAPL.currentSharePrice=4.50;
        AAPL.numberOfShares=40;
        [stockArray addObject:AAPL];


        GOOG.purchaseSharePrice=12.19;
        GOOG.currentSharePrice=10.56;
        GOOG.numberOfShares=90;
        [stockArray addObject:GOOG];


        NYSE.purchaseSharePrice=45.10;
        NYSE.currentSharePrice=49.51;
        NYSE.numberOfShares=210;
        [stockArray addObject:NYSE];

        BNRForeignStockHolding *conv = [[BNRForeignStockHolding alloc]init];
        conv.converstionRate = 0.5;


        for (BNRForeignStockHolding *d in stockArray)
        {
            float currentTotalPrice = d.costInDollars;
            float purchasedTotalPrice = d.valueInDollars;

            NSLog(@"Purchased:$%f \n\t\t\t\t\t\t\t\t\t\t Valued:$%f",currentTotalPrice, purchasedTotalPrice);



        }



    }
    return 0;
}

我正在尝试覆盖子类.m中的方法costInDollars和valueInDollars，同时实现对float的conversionRate。

我的主要是从原始类中获取方法，而不是子类，并且它们没有被覆盖。

抱歉 - 谢谢。

Answer 1

简单地将每种类型转换为BNRForeignStockHolding不会改变它们的具体类型。在提供的代码中，您只需向NSArray添加BNRStockHolding个实例。你可以在增强的for循环中通过编译器的原因是因为动态绑定 - NSArray没有任何类型的知识，因此编译器只能假设它们充满了id。允许您在运行时访问costInDollars的原因是因为基类碰巧响应该选择器，但它们在运行时不是BNRForeignStockHolding类型。

如果您需要这些结果，则需要将所有[[BNRStockHolding alloc] init]更改为[[BNRForeignStockHolding alloc] init]并在每个实例上设置conversionRate。

<强>替代

如果conversionRate可以是全局的，那么您可以添加类getter / setter。

实施例。在BNRForeignStockHolding.m：

static _conversionRate;
+ (void)setConversionRate:(float)conversionRate {
    _conversionRate = conversionRate;
}

+ (float)conversionRate {
    return _conversionRate;
}

然后在实例方法中：

-(float)costInDollars{
    float normalCost = [super costInDollars];
    return normalCost*[self.class conversionRate];
}

-(float)valueInDollars{
    float normalValue = [super valueInDollars];
    return normalValue*[self.class conversionRate];
}

并在您的实施中：

[BNRForeignStockHolding setConversionRate:0.5];

覆盖子类中的两个方法

1 个答案: