Objective-C練習未聲明的標識符錯誤

Question

我目前在教自己Objective-C作爲第一語言。我明白所涉及的困難，但我卻是一個堅忍不拔的人。我已經開始在Apple Objective-C文檔上進行練習。我的目標是讓我的程序註銷我的名字和姓氏，而不是通用的Hello World問候語。

我不斷收到使用未聲明的標識符錯誤。我試圖找出是什麼導致了錯誤。

這裏是introClass.h

#import <UIKit/UIKit.h> 

    @interface XYZperson : NSObject 

    @property NSString *firstName; 
    @property NSString *lastName; 
    @property NSDate *dateOfBirth; 
    - (void)sayHello; 
    - (void)saySomething:(NSString *)greeting; 
    + (instancetype)person; 
    -(int)xYZPointer; 
    -(NSString *)fullName; 
    @end 

這裏是IntroClass.m

#import "IntroClass.h" 

@implementation XYZperson 
-(NSString *)fullName 
{ 
    return[NSString stringWithFormat:@" %@ %@", self.firstName, self.lastName]; 
} 

-(void)sayHello 
{ 
    [self saySomething:@"Hello %@", fullName]; //use of undeclared identifier "fullName" 
}; 

-(void)saySomething:(NSString *)greeting 
{ 
    NSLog(@"%@", greeting); 
} 

+(instancetype)person{ 
    return [[self alloc] init]; 
}; 

- (int)xYZPointer { 
    int someInteger; 
    if (someInteger != nil){ 
     NSLog(@"its alive"); 
    } 
    return someInteger; 
}; 


@end 

Answer 1

的問題是，fullName是一個方法的名稱。應在0​​上用方括號調用。

由於saySomething:需要一個單一的參數，則需要：（1）除去該呼叫的@"Hello %@"部分，像這樣：

-(void)sayHello { 
    [self saySomething:[self fullName]]; 
}; 

，或者從@"Hello %@"和[self fullName]，這樣使一個單一的字符串：

-(void)sayHello { 
    [self saySomething:[NSString stringWithFormat:@"Hello %@", [self fullName]]]; 
}; 

Answer 2

使用

[self saySomething:@"Hello %@", self.fullName]]; 

或

[self saySomething:@"Hello %@", [self fullName]]; 

Answer 3

您傳回的姓和名的字符串，但我沒有看到任何地方，你已經爲他們設定的值。正如其他人指出嘗試

-(void)sayHello 
    { 
     _firstName = [NSString stringWithFormat:@"John"]; 
     _lastName = [NSString stringWithFormat:@"Doe"]; 

     //if you want to see what's happening through out your code, NSLog it like 
     NSLog(@"_firstName: %@ ...", _firstName); 
     NSLog(@"_lastName: %@ ...", _lastName); 

     NSString *strReturned = [self fullName]; 
     NSString *concatStr = [NSString stringWithFormat:@"Hello %@", strReturned]; 

     NSLog(@"strReturned: %@ ...", strReturned); 
     NSLog(@"concatStr: %@ ...", concatStr); 

     [self saySomething:concatStr]; 
    }; 

    -(NSString *)fullName 
    { 
     return[NSString stringWithFormat:@" %@ %@", self.firstName, self.lastName]; 
    }