objective-c - 设置记录数组数据时要调用的类标识符

Question

嘿 stackOverflow 社区。我正在阅读 Big Nerd Ranch 的 Objective C 书，并且遇到了有关定义和设置类的有趣章节(如果您熟悉的话，请参阅第 17 章)。其中的挑战是我们编写一个程序，在其中定义一个具有多个属性和实例变量的股票类。我已经能够让程序按照要求工作，但我想稍微修改一下，让它也 NSLog a stockName，这样我就可以看到哪些股票与其属性相关联。

基本上，有没有办法让这个 block 的代码更加简洁:

NSString *appleName = @"AppleInc";
[Apple setStockIdentifier:appleName];

也许更像这样:

[Apple setStockIdentifier:"AppleInc"];

我尝试在类文件中将属性设置为字符，但无法使其工作。我对此很陌生，但我认为为 stockIdentifier 值声明一个新的 NSString 是不需要的额外代码。任何反馈将不胜感激。

以下是我的主文件:

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

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

@autoreleasepool {

    StockHolding *Apple = [[StockHolding alloc] init];
    NSString *appleName = @"AppleInc";
    [Apple setStockIdentifier:appleName];
    [Apple setPurchaseSharePrice:2.30];
    [Apple setCurrentSharePrice:4.50];
    [Apple setNumberOfShares:40];

    StockHolding *HomeDepot = [[StockHolding alloc] init];
    NSString *homeDepotName = @"Home Depot Inc";
    [HomeDepot setStockIdentifier:homeDepotName];
    [HomeDepot setPurchaseSharePrice:12.19];
    [HomeDepot setCurrentSharePrice:10.56];
    [HomeDepot setNumberOfShares:90];

    StockHolding *Cisco = [[StockHolding alloc] init];
    NSString *ciscoName = @"Cisco Inc";
    [Cisco setStockIdentifier:ciscoName];
    [Cisco setPurchaseSharePrice:45.10];
    [Cisco setCurrentSharePrice:49.51];
    [Cisco setNumberOfShares:210];

    NSMutableArray *listOfStocks = [NSMutableArray arrayWithObjects:Apple, HomeDepot, Cisco, nil];

    for (StockHolding *currentStock in listOfStocks) {
        NSLog(@"%@, Purchase Share Price: %.2f; Current value: %.2f; Number of shares: %i",[currentStock stockIdentifier],[currentStock purchaseSharePrice], [currentStock currentSharePrice], [currentStock numberOfShares]);
    }


}
return 0;
}

以下是StockHolding.h的内容:

#import <Foundation/Foundation.h>

@interface StockHolding : NSObject

{
//char stockIdentifier;
float purchaseSharePrice;
float currentSharePrice;
int numberOfShares;
}

@property NSString *stockIdentifier;
@property float purchaseSharePrice;
@property float currentSharePrice;
@property int numberOfShares;

-(float) costInDollars; //purchaseSharePrice * numberOfShares;
-(float) valueInDollars; //currentSharePrice * numberOfShares;

@end

这里是 StockHolding.m:

#import "StockHolding.h"

@implementation StockHolding

@synthesize currentSharePrice, purchaseSharePrice, numberOfShares, stockIdentifier;

-(float)costInDollars;
{
return (purchaseSharePrice * numberOfShares);
}

-(float)valueInDollars;
{
return (currentSharePrice * numberOfShares);
}

@end

Answer 1

这只是一个语法错误。

[Apple setStockIdentifier:"AppleInc"];

应该是...

[Apple setStockIdentifier:@"AppleInc"];