未知类型名称'TransportViewController'

Question

这可能是一个简单的错误，但我似乎无法找出错误Unknown type name 'TransportViewController'的错误。我试图通过xCoor和yCoor这是2 double值到我的第二个视图是TransportViewController。这里是我的代码：

TransportViewController *xCoor; 
TransportViewController *yCoor; 
@property (retain, nonatomic) TransportViewController *xCoor; 
@property (retain, nonatomic) TransportViewController *yCoor; 

这4行是给我的错误

MapViewController.h文件

#import "TransportViewController.h" 
@interface MapViewController : UIViewController{ 
    TransportViewController *xCoor; 
    TransportViewController *yCoor; 
} 
@property (retain, nonatomic) TransportViewController *xCoor; 
@property (retain, nonatomic) TransportViewController *yCoor; 

MapViewController.m文件

#import "TransportViewController.h" 
@implementation MapViewController 
@synthesize xCoor; 
@synthesize yCoor; 
. 
. 
. 
- (IBAction) publicTransportAction:(id)sender{ 
    TransportViewController *view = [[TransportViewController alloc] initWithNibName:nil bundle:nil]; 
    self.xCoor = view; 
    self.yCoor = view; 
    xCoor.xGPSCoordinate = self.mapView.gps.currentPoint.x; 
    yCoor.xGPSCoordinate = self.mapView.gps.currentPoint.y; 
    [self presentModalViewController:view animated:NO]; 
} 

TransportViewController.h文件

#import "MapViewController.h" 
@interface TransportViewController : UIViewController<UITextFieldDelegate> 
{ 
    double xGPSCoordinate; 
    double yGPSCoordinate; 
} 
@property(nonatomic)double xGPSCoordinate; 
@property(nonatomic)double yGPSCoordinate; 
@end 

Answer 1

你有一个循环依赖。总之，你已指示编译：

• MapViewController.h需要TransportViewController.h
• 和TransportViewController.h需要MapViewController.h

实际上 - 既不是在头必要的。在这两种情况下，您都可以使用转发声明。

MapViewController.h

@class TransportViewController; // << forward declaration instead of inclusion 

@interface MapViewController : UIViewController { 
    TransportViewController *xCoor; 
    TransportViewController *yCoor; 
} 
@property (retain, nonatomic) TransportViewController *xCoor; 
@property (retain, nonatomic) TransportViewController *yCoor; 
@end 

TransportViewController.h

@class MapViewController; // << not even needed, as MapViewController 
          // does not exist in this header 

@interface TransportViewController : UIViewController<UITextFieldDelegate> 
{ 
    double xGPSCoordinate; 
    double yGPSCoordinate; 
} 
@property(nonatomic)double xGPSCoordinate; 
@property(nonatomic)double yGPSCoordinate; 
@end 

那么你#import S可在*.m文件去需要的地方。

你应该阅读前瞻性声明。你不能在任何地方使用它们，但是你可以在头文件中使用它们而不是#import，这样可以真正减少构建时间。