不兼容的 Objective-c 类型警告

Question

我有一个通过 iPhone 应用程序使用的用户类，这是我的用户类（NSobject 的子类）中的 init 和 initWithUser 函数，当我使用 initWithUser 函数时，我收到代码后描述的警告。请指教。

// serialize.h 
#import <Foundation/Foundation.h>

@protocol Serialize

// serialize the object to an xml string
-(NSString*)ToXML;

@end


// user.h
#import <Foundation/Foundation.h>
#import "Serialize.h"
#import "Contact.h"


@interface User : NSObject <Serialize> {

NSString *email;
NSString *firstName;
NSString *lastName;
NSString *userId;
NSString *userName;
NSString *password;

NSMutableArray *contactList;

}

@property (nonatomic,copy) NSString *email;
@property (nonatomic,copy) NSString *firstName;
@property (nonatomic,copy) NSString *lastName;
@property (nonatomic,copy) NSString *userId;
@property (nonatomic,copy) NSString *userName;
@property (nonatomic,copy) NSString *password;
@property (nonatomic, retain) NSMutableArray *contactList;

//-(id)init;
-(id)initWithUser:(User *)copyUser;

@end



// user.m 
#import "user.h"


@implementation User

@synthesize email;
@synthesize firstName;
@synthesize lastName;
@synthesize userId;
@synthesize userName;
@synthesize password;
@synthesize contactList;

-(id)init
{
    // call init in parent and assign to self
    if( (self = [super init]) ) 
    {          
        // do something specific 
        contactList = [[NSMutableArray alloc] init];

    }
    return self;
}

-(id)initWithUser:(User *)copyUser
{
    if( (self = [self init]) ) {           

        email               = copyUser.email;
        firstName           = copyUser.firstName;
        lastName            = copyUser.lastName;
        userId              = copyUser.userId;
        userName            = copyUser.userName;
        password            = copyUser.password;

        // release contactList initialized in the init
        [contactList release];
        contactList         = [copyUser.contactList mutableCopy];
    }

    return self;
}

- (void)dealloc
{
    // TODO: 
    [contactList removeAllObjects];
    [contactList release];
    [super dealloc];
}

// implementation of serialize protocol
-(NSString*)ToXML
{
    return @""; 
}

我在主控制器中这样使用它

- (void) registerNewUser {

    RegistrationViewController *regController = [[RegistrationViewController alloc] init] ;

    regController.newUser = [[User alloc] initWithUser:self.user];

    [self.navigationController pushViewController:regController animated:YES];
    [regController release];

}

一行

regController.newUser = [[User alloc] initWithUser:self.user];

给我以下错误，这几天让我发疯：

不兼容的 Objective-c 类型 'struct User*'，当从不同的 Objective-c 类型传递 'initWithUser:' 的参数 1 时需要 'struct NSString *'

感谢任何帮助和指导

Answer 1

如 cmets 中所述，您的实施还存在其他问题。在您的初始化程序中，重用 -init 是多余的，并且分配给像 email 这样的 ivars 应该使用 -copy 或 -retain 获得数据的所有权：

-(id)initWithUser:(User *)copyUser {
    if((self = [super init])) {
        // take ownership of the users data by copying or retaining:
        email = [copyUser.email copy];
        // ...

        contactList = [copyUser.contactList mutableCopy];
    }    
    return self;
}

在-dealloc中，-removeAllObjects可以被移除，会员数据要发布：

- (void)dealloc {
    [email release];
    // ...

    [contactList release];
    [super dealloc];
}

请注意，如果newUser 是copy 或retain 属性，您也会泄漏新的User 实例，因为缺少release：

User *user = [[User alloc] initWithUser:self.user];
regController.newUser = user;
[user release];

Answer 2

问题是你有一个模棱两可的选择器。因为alloc 返回id，所以对initWithUser: 的调用变得模棱两可。 NSUserDefaults 也有一个 initWithUser: 函数，它接受一个字符串。编译器认为您正在尝试使用那个。将行改为

regController.newUser = [(User*)[User alloc] initWithUser:self.user];

一切都应该按预期工作。