objective-c - 持久 '' 可能无法响应 +method

Question

我发现了很多关于这个问题的帖子，并且实际上已经成功删除了我从这些帖子中收到的一个警告，但其中一个警告仍然存在。

一些背景:我正在创建货币转换器作为学习 Objective C 的练习

我的汇率类别表示货币可以相互转换的汇率，如下所示:

Rate.h

//
//  Rate.h
//  Currency Converter
//
//  Created by Matthew Spence on 08/06/2010.
//  Copyright 2010 __MyCompanyName__. All rights reserved.
//

#import <Cocoa/Cocoa.h>


@interface Rate : NSObject {
NSString* code;
NSString* description;
float rate;
}
- (id)init;
- (id)initTest;
- (id)initWithCode:(NSString*)code description:(NSString*)description  rate:(float)rate;
@property(retain) NSString* code;
@property(retain) NSString* description;
@property(readwrite) float rate;
@end

评分.m

//
//  Rate.m
//  Currency Converter
//
//  Created by Matthew Spence on 08/06/2010.
//  Copyright 2010 __MyCompanyName__. All rights reserved.
//

#import "Rate.h"


@implementation Rate
@synthesize code;
@synthesize description;
@synthesize rate;
- (id)init {
return self;
}

- (id)initTest {
return self;
}

- (id)initWithCode:(NSString*)codeA description:(NSString*)descriptionA  rate:(float)rateA {
self.code = codeA;
self.description = descriptionA;
self.rate = rateA;
[self init];
return self;
}
@end

警告发生在 ExchangeRates 中，这是一个包含费率矩阵的单例类:

汇率.m

//
//  ExchangeRates.m
//  Currency Converter
//
//  Created by Matthew Spence on 02/06/2010.
//  Copyright 2010 __MyCompanyName__. All rights reserved.
//

#import "ExchangeRates.h"
#import "SynthesizeSingleton.h"
#import "Rate.h"
#import "NSString+CVS.h"


@implementation ExchangeRates
@synthesize matrix;
synthesize_singleton(ExchangeRates);
- (id)init {

self = [super init];
self.matrix = [NSMapTable init];
    if (self) {
    NSError *error = nil;
    NSString *matrixString = [NSString stringWithContentsOfURL:[NSURL URLWithString:@"http://rss.timegenie.com/forex.txt"] encoding:NSUTF8StringEncoding error:&error];
    NSArray *matrixArray = [matrixString csvRows];
    for(NSArray *rateArray in matrixArray) {
        Rate *rate = [Rate initWithCode:[rateArray objectAtIndex:0] description:[rateArray objectAtIndex:1] rate:[rateArray objectAtIndex:2]];
        [self.matrix setObject:rate forKey:[rateArray objectAtIndex:0]] ;
        NSLog(@"my ns string = %@", [rateArray objectAtIndex:0]);
    }
    }

    return self;
}
@end

上线:

Rate *rate = [Rate initWithCode...

警告:

'Rate' may not respond to '+initWithCode:description:rate:'

据我了解，这通常是由于未在 header 中声明方法或未导入 header ，但如您所见，我已经完成了这两件事。

Answer 1

您应该将 ObjC 实例初始化为

Rate* rate = [[Rate alloc] initWithCode:...];
//                  ^^^^^