Question

我是客观c编码的新手，请耐心问我是否这是一个简单的问题。

当我尝试运行下面的代码时，它说

NO visible @interface for 'SampleClass' declares the selector 'multiplyA:withB'

在目标C中乘以两个数字是错误的方法吗？我无法找到错误。

这是代码的头文件

    #import <Cocoa/Cocoa.h>

    @interface AppDelegate : NSObject <NSApplicationDelegate>

    @property (assign) IBOutlet NSWindow *window;

    @end

    @interface SampleClass : NSObject

    -(NSNumber *)multiplYA:(NSNumber *)a withB:(NSNumber *)b;

    @end

这是代码的实现文件

    #import "AppDelegate.h"

    @implementation AppDelegate

    - (void)applicationDidFinishLaunching:(NSNotification *)aNotification
   {
               // Insert code here to initialize your application


               SampleClass *sampleClass = [[SampleClass alloc]init];
               NSNumber *a = [NSNumber numberWithFloat:10.5];
               NSNumber *b = [NSNumber numberWithFloat:10.0];


               NSNumber *result = [sampleClass multiplyA:a withB:b];


               NSString *resultString = [result stringValue];
               NSLog(@"The product is %@",resultString);


          }

           @end


          @implementation SampleClass

          - (NSNumber *)multiplyA:(NSNumber *)a withB:(NSNumber *)b
      {
               float number1 = [a floatValue];
               float number2 = [b floatValue];
               float product = number1 * number2;
               NSNumber *result = [NSNumber numberWithFloat:product];
               return result;
       }
          @end

Answer 1

这是头文件中的大小写。将标题函数标题更改为：

-(NSNumber *)multiplyA:(NSNumber *)a withB:(NSNumber *)b;

Answer 2

您只需在multiplyA:withB部分提供@interface方法声明即可。现在它读取-(NSNumber *)multiplYA:(NSNumber *)a withB:(NSNumber *)b;。看到错误？大Y.它一定很小。或者其他 - @implementation部分内的大Y.换句话说，他们应该匹配

ARC语义问题

2 个答案: