NSMutableDictionary not retrieve object

Question

EmployeesArray = [[NSMutableArray alloc] initWithCapacity:100]; 
    Employees *Emp1 = [[Employees alloc] init];  
    Emp1.Number = 1; 
    Emp1.Name = @"Jamal"; 
    Emp1.Age = 16; 
    Emp1.Gender = @"Male"; 
    [EmployeesArray addObject:Emp1]; 
[Dic1 setValue:Emp1 forKey:@"A"]; 

- (IBAction)Retrieve:(id)sender { 

    Employees *objEmp2 = [Dic1 valueForKey:@"A"]; 
    printf(objEmp2.Name); 

} 

爲什麼這段代碼沒有檢索到名字？並出現錯誤？

Answer 1

你初始化了Dic1字典？

// try doing this 
Dic1 = [[NSMutableDictionary alloc] init]; 

EmployeesArray = [[NSMutableArray alloc] initWithCapacity:100]; 
    Employees *Emp1 = [[Employees alloc] init];  
    Emp1.Number = 1; 
    Emp1.Name = @"Jamal"; 
    Emp1.Age = 16; 
    Emp1.Gender = @"Male"; 
    [EmployeesArray addObject:Emp1]; 
[Dic1 setObject:Emp1 forKey:@"A"]; 

- (IBAction)Retrieve:(id)sender { 

    Employees *objEmp2 = [Dic1 objectForKey:@"A"]; 
    printf(objEmp2.Name); 

} 

Answer 2

有三件事可能會有幫助。使用

1. -setObject:forKey:代替-setValue:forKey 使用objectForKey代替valueForKey因爲您使用自定義類。
2. 一般來說，使用objective-c風格-NSLog()而不是c風格的代碼會更容易。
3. 確保已導入包含Employees類定義的頭文件，而不是將其用作當前.m文件的前向類。

Answer 3

您需要使用setObject:forKey和objectForKey:方法而不是setValue:forKey:和valueForKey: