Xcode 編譯錯誤: duplicate symbols for architecture arm64

在編譯的時候編譯失敗，並且查詢錯誤訊息：duplicate symbols for architecture arm64

於是我到專案→Target→Build Phases→Complie Source 卻沒有重複的 .m檔，我將過去的專案設定做比對，發現 Build Setting 的 No common blocks 與先前的專案設定不一樣，改為 No 便可以編譯通過。

Apple Quick Help 解釋 No common blocks：

Declaration: GCC_NO_COMMON_BLOCKS
	Description: In C, allocate even uninitialized global variables in the data section of the object file, rather than generating them as common blocks.  This has the effect that if the same variable is declared (without extern ) in two different compilations, you will get an error when you link them. [GCC_NO_COMMON_BLOCKS, -fno-common]

Xcode 6.1.3 上架失敗

解決辦法：

把裝置從 Macbook 上拔除，直接 Archive

繼承至 NSManagedobject 的 Entity 當作一般物件使用

NSEntityDescription *entityDescription = [NSEntityDescription entityForName:@"Device" inManagedObjectContext:[[WPCoreDataCenter sharedMainCenter] mainManagedObjectContext]];
Device *device = [[Device alloc] initWithEntity:entityDescription insertIntoManagedObjectContext:nil];
device.idnum = @"A845dd7412b56";
device.serial = @"SMACODZL";

亂數產生器

int generateRandomNumberBetweenMin(int min,int max)
{
    return ( (arc4random() % (max-min+1)) + min );
}