Xcode4 从另一个viewController写入全局数组

我在一个viewController中有一个数组，我想从另一个viewController写入该数组，所以我将该数组定义为全局数组，但我没有成功写入它

ViewController1.h

extern NSArray *xArray;
@property (nonatomic, retain) NSArray *xArray;

NSArray *xArray;
..
@property (nonatomic, retain) NSArray *xArray;
..
@synthesize *xArray;

ViewController1.m

@synthesize xArray;
NSArray *xArray;
xArray = [[NSArray alloc] init];

#import "ViewController1.h"
NSArray *zArray = [NSArray arrayWithObjects:@"a",@"b",nil];
ViewController1.xArray = zArray;

NSArray *tmpArray1;
AppDelegate *mainDelegate = (AppDelegate *)[[UIApplication sharedApplication] delegate];
mainDelegate.xArray = tmpArray1;

NSArray *tmpArray2;
AppDelegate *mainDelegate = (AppDelegate *)[[UIApplication sharedApplication] delegate];
mainDelegate.xArray = tmpArray2;

ViewController2.m

@synthesize xArray;
NSArray *xArray;
xArray = [[NSArray alloc] init];

#import "ViewController1.h"
NSArray *zArray = [NSArray arrayWithObjects:@"a",@"b",nil];
ViewController1.xArray = zArray;

NSArray *tmpArray1;
AppDelegate *mainDelegate = (AppDelegate *)[[UIApplication sharedApplication] delegate];
mainDelegate.xArray = tmpArray1;

NSArray *tmpArray2;
AppDelegate *mainDelegate = (AppDelegate *)[[UIApplication sharedApplication] delegate];
mainDelegate.xArray = tmpArray2;

我得到以下错误：

---

在“ViewController1”类型的对象上找不到属性“xArray”

找到解决方案，在应用程序委托中定义数组，并在任何类中使用它

AppDelegate.h

extern NSArray *xArray;
@property (nonatomic, retain) NSArray *xArray;

NSArray *xArray;
..
@property (nonatomic, retain) NSArray *xArray;
..
@synthesize *xArray;

ViewController1.m

@synthesize xArray;
NSArray *xArray;
xArray = [[NSArray alloc] init];

#import "ViewController1.h"
NSArray *zArray = [NSArray arrayWithObjects:@"a",@"b",nil];
ViewController1.xArray = zArray;

NSArray *tmpArray1;
AppDelegate *mainDelegate = (AppDelegate *)[[UIApplication sharedApplication] delegate];
mainDelegate.xArray = tmpArray1;

NSArray *tmpArray2;
AppDelegate *mainDelegate = (AppDelegate *)[[UIApplication sharedApplication] delegate];
mainDelegate.xArray = tmpArray2;

ViewController2.m

@synthesize xArray;
NSArray *xArray;
xArray = [[NSArray alloc] init];

#import "ViewController1.h"
NSArray *zArray = [NSArray arrayWithObjects:@"a",@"b",nil];
ViewController1.xArray = zArray;

NSArray *tmpArray1;
AppDelegate *mainDelegate = (AppDelegate *)[[UIApplication sharedApplication] delegate];
mainDelegate.xArray = tmpArray1;

NSArray *tmpArray2;
AppDelegate *mainDelegate = (AppDelegate *)[[UIApplication sharedApplication] delegate];
mainDelegate.xArray = tmpArray2;