iOS - 3 duplicate symbols for architecture i386

问题

I am having an issue understanding a linker command error. I am receiving the following:

duplicate symbol _OBJC_IVAR_$_XYZAddToDoItemViewController._toDoItem in:
/Users/*/Library/Developer/Xcode/DerivedData/ToDoToday-fjyijxlbvauebmeuhtgdvdrjtfez/Build/Intermediates/ToDoToday.build/Debug-iphonesimulator/ToDoToday.build/Objects-normal/i386/XYZToDoListViewController.o
/Users/*/Library/Developer/Xcode/DerivedData/ToDoToday-fjyijxlbvauebmeuhtgdvdrjtfez/Build/Intermediates/ToDoToday.build/Debug-iphonesimulator/ToDoToday.build/Objects-normal/i386/XYZAddToDoItemViewController.o
duplicate symbol _OBJC_CLASS_$_XYZAddToDoItemViewController in:
/Users/*/Library/Developer/Xcode/DerivedData/ToDoToday-fjyijxlbvauebmeuhtgdvdrjtfez/Build/Intermediates/ToDoToday.build/Debug-iphonesimulator/ToDoToday.build/Objects-normal/i386/XYZToDoListViewController.o
/Users/*/Library/Developer/Xcode/DerivedData/ToDoToday-fjyijxlbvauebmeuhtgdvdrjtfez/Build/Intermediates/ToDoToday.build/Debug-iphonesimulator/ToDoToday.build/Objects-normal/i386/XYZAddToDoItemViewController.o
duplicate symbol _OBJC_METACLASS_$_XYZAddToDoItemViewController in:
/Users/*/Library/Developer/Xcode/DerivedData/ToDoToday-fjyijxlbvauebmeuhtgdvdrjtfez/Build/Intermediates/ToDoToday.build/Debug-iphonesimulator/ToDoToday.build/Objects-normal/i386/XYZToDoListViewController.o
/Users/*/Library/Developer/Xcode/DerivedData/ToDoToday-fjyijxlbvauebmeuhtgdvdrjtfez/Build/Intermediates/ToDoToday.build/Debug-iphonesimulator/ToDoToday.build/Objects-normal/i386/XYZAddToDoItemViewController.o
ld: 3 duplicate symbols for architecture i386
clang: error: linker command failed with exit code 1 (use -v to see invocation)

I'm not sure which symbols Xcode is referring to exactly. Below are the top of the implementation files.

XYZToDoListViewController.m:

#import "XYZAddToDoItemViewController.h"
@interface XYZAddToDoItemViewController ()
@property NSMutableArray *toDoItems;
@end
@implementation XYZAddToDoItemViewController

XYZAddToDoItemViewController.m:

#import "XYZAddToDoItemViewController.h"
@interface XYZAddToDoItemViewController ()
@property (weak, nonatomic) IBOutlet UITextField *textField;
@property (weak, nonatomic) IBOutlet UIBarButtonItem *doneButton;
@end
@implementation XYZAddToDoItemViewController

Any help would be much appreciated, thank you.

回答1:

In your XYZToDoListViewController.m change:

@interface XYZAddToDoItemViewController ()

to:

@interface XYZToDoListViewController ()

and:

@implementation XYZAddToDoItemViewController

to:

@implementation XYZToDoListViewController

and:

#import "XYZAddToDoItemViewController.h"

to:

#import "XYZToDoListViewController.h"

Basically you have the wrong class name in the XYZToDoListViewController.m file.

Make you don't have the same mistake in the XYZToDoListViewController.h file.

回答2:

I encounter this error when I import A.m in B.m

Make sure you only import .h files

来源：https://stackoverflow.com/questions/19941747/ios-3-duplicate-symbols-for-architecture-i386