程序接收信號“EXC_Bad_Access”NSMutableArray

Question

如果我嘗試重新運行下面的代碼，我會在 [categoryList count] 上收到一條 EXE_bad_access 消息

NSMutableArray *categoryList = [[CategoryItem alloc] getAll];
NSLog(@"number of items is %@", [categoryList count]);

class 如下

#import "CategoryItem.h"

#import "SQLite.h"

@interface CategoryItem : NSObject {
    NSInteger ID;
    NSInteger SortOrder;
    NSString *Name;
    NSString *ShoppingImage;

}

@property (nonatomic, nonatomic) NSInteger SortOrder;
@property (nonatomic, retain) NSString * Name;
@property (nonatomic, retain) NSString * ShoppingImage;
@property (nonatomic, nonatomic) NSInteger ID;

- (id)initWithObject:(NSInteger)itemID;
-(NSMutableArray *)getAll;

@end
@implementation CategoryItem


@synthesize ShoppingImage;
@synthesize Name;
@synthesize ID;
@synthesize SortOrder;

- (id)initWithObject:(NSInteger)itemID {

    if ((self = [super init])) {
        sqlite3 *database;
        // Open the database. The database was prepared outside the application.
        if (sqlite3_open([[SQLite fullFilePath] UTF8String], &database) == SQLITE_OK) {
            // Get the primary key for all books.
            const char *sql = "SELECT ID, Name, ShoppingImage, SortOrder FROM CategoryItem WHERE ID =?";
            sqlite3_stmt *statement;
            // Preparing a statement compiles the SQL query into a byte-code program in the SQLite library.
            // The third parameter is either the length of the SQL string or -1 to read up to the first null terminator.        
            if (sqlite3_prepare_v2(database, sql, -1, &statement, NULL) == SQLITE_OK) {
                // We "step" through the results - once for each row.
                sqlite3_bind_int(statement, 1, itemID);

                while (sqlite3_step(statement) == SQLITE_ROW) {
                    // The second parameter indicates the column index into the result set.
                    self.ID = itemID;
                    self.Name = [NSString stringWithUTF8String:(char *)sqlite3_column_text(statement, 1)];
                    self.ShoppingImage = [NSString stringWithUTF8String:(char *)sqlite3_column_text(statement, 2)];
                    self.SortOrder = sqlite3_column_int(statement, 3);
                }
            }
            // "Finalize" the statement - releases the resources associated with the statement.
            sqlite3_finalize(statement);
        } else {
            // Even though the open failed, call close to properly clean up resources.
            sqlite3_close(database);
            NSLog(@"Failed to open database with message '%s'.", sqlite3_errmsg(database));
            // Additional error handling, as appropriate...
        }

    }
    return self;
}

-(NSMutableArray*)getAll{

    NSMutableArray *listArray = [[[NSMutableArray alloc] init] autorelease];

    sqlite3 *database;
    // Open the database. The database was prepared outside the application.
    if (sqlite3_open([[SQLite fullFilePath] UTF8String], &database) == SQLITE_OK) {
        // Get the primary key for all books.
        const char *sql = "SELECT ID, Name, ShoppingImage, SortOrder FROM CategoryItem ORDER BY SortOrder";
        sqlite3_stmt *statement;
        // Preparing a statement compiles the SQL query into a byte-code program in the SQLite library.
        // The third parameter is either the length of the SQL string or -1 to read up to the first null terminator.

        if (sqlite3_prepare_v2(database, sql, -1, &statement, NULL) == SQLITE_OK) 
        {

            // We "step" through the results - once for each row.
            while (sqlite3_step(statement) == SQLITE_ROW)
            {
                // The second parameter indicates the column index into the result set.

                CategoryItem *categoryItem = [[CategoryItem alloc] init];

                categoryItem.ID = sqlite3_column_int(statement, 0);
                categoryItem.Name = [NSString stringWithUTF8String:(char *)sqlite3_column_text(statement, 1)];
                categoryItem.ShoppingImage = [NSString stringWithUTF8String:(char *)sqlite3_column_text(statement, 2)];
                categoryItem.SortOrder = sqlite3_column_int(statement, 3);

                [listArray addObject:categoryItem];

                [categoryItem release];
                categoryItem = nil;

            }


        }else{
            printf( "could not prepare statemnt: %s\n", sqlite3_errmsg(database) ); 
        }
        // "Finalize" the statement - releases the resources associated with the statement.
        sqlite3_finalize(statement);

    } else {
        // Even though the open failed, call close to properly clean up resources.
        sqlite3_close(database);
        NSLog(@"Failed to open database with message '%s'.", sqlite3_errmsg(database));
        // Additional error handling, as appropriate...
    }

    //NSLog(@"this is the list array count %@", [listArray count]);

    return listArray;
}



- (void)dealloc {
    [super dealloc];
    [Name release];
    [ShoppingImage release];

}


@end

Answer 1

您創建CategoryItem的方式似乎不正確。 您正在調用alloc但不是任何init...方法。 您可能希望使用您在實現中提供的initWithObject方法。

來自蘋果文檔：

使用 Objective-C 創建 object 需要兩個步驟。 你必須：

• 為新的 object 動態分配 memory

• 將新分配的 memory 初始化為合適的值

在完成這兩個步驟之前，object 不能完全正常工作。 每個步驟都由一個單獨的方法完成，但通常在一行代碼中：

id anObject = [[矩形分配] init];

編輯：

除了初始化問題之外，似乎還有一個概念問題（@Terry Wilcox 指出）：在實例上調用方法getAll似乎沒有意義，因此應該定義為 class 方法：

+ (NSMutableArray*)getAll;

應該這樣稱呼：

NSMutableArray *categoryList = [CategoryItem getAll];

編輯2：

您的日志語句似乎也不正確。 [categoryList count]返回NSUInteger並且您正在嘗試使用%@打印 object 。 使用%i代替：

NSLog(@"number of items is %i", [categoryList count]);

Answer 2

這段代碼：

NSMutableArray *categoryList = [[CategoryItem alloc] getAll];

沒有意義。 如果 getAll 是 CategoryItem 上的 class 方法，則應將其定義為

+ (NSMutableArray*)getAll;

你應該把它稱為

NSMutableArray *categoryList = [CategoryItem getAll];

那么 categoryList 將是一個您不擁有的數組，因此您可能希望在獲得它時保留它。