iOS数据库存取复杂类型数组

在项目实现中经常遇到会用数据库存取图片/音频/视频等复杂类型数组,当数组count确定时,可以根据个数存取,但大部分时候数组的个数是不能确定的.

这时,我们就可以利用归档/反归档,把复杂类型转为数据库可存取的Data类型,来方便使用,下面本文以图片数组为例,简单的介绍下具体实现方法.

sqlite不支持存取复杂类型,但它为我们提供了BLOB类型,来存取Data类型.需要注意的是,如果直接把图片数组归档为Data存进sqlite,是存不进去的.我们需要先把数组中的每个图片转为Data,存入数组,再把装有所有图片Data的数组归档为Data,并以BLOB类型存入sqlite,才可以实现.

大致的思路就是这样的,下面代码跟上~~

static DataManager *dataBase = nil;
static FMDatabase *db = nil;

+(instancetype)sharedDataBase{
    
    @synchronized(self) {
        
        if (nil == dataBase) {
            dataBase = [[DataManager alloc]init];
            [dataBase openDB];
        }
    }
    return dataBase;
}

// 打开数据库
- (void)openDB{
    
    if (nil != db) {
        return;
    }
    
    NSString *documentPath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) firstObject];
    NSLog(@"%@",documentPath);
    documentPath = [documentPath stringByAppendingPathComponent:@"/student.sqlite"];
    
    db = [FMDatabase databaseWithPath:documentPath];
    
    if ([db open]) {
        
        BOOL result = [db executeUpdate:@"CREATE TABLE IF NOT EXISTS Student ('ID' TEXT PRIMARY KEY NOT NULL, 'name' TEXT NOT NULL, 'age' TEXT NOT NULL, 'imgArray' BLOB);"];
        
        if (result) {
            NSLog(@"数据库打开成功!");
        }else{
            NSLog(@"数据库打开失败!");
        }
    }
}



// 往数据库插入model
- (void)insertStudentWithModel:(StudentModel *)model{
    
    // img 转 imgData
    NSMutableArray *imgDataArray = [NSMutableArray arrayWithCapacity:5];
    for (UIImage *img in model.imgArray) {
        NSData *imgData = UIImageJPEGRepresentation(img, 1);
        [imgDataArray addObject:imgData];
    }
    
    // imgArray归档
    NSMutableData * imgArrayData = [NSMutableData dataWithCapacity:500];
    NSKeyedArchiver * archiver = [[NSKeyedArchiver alloc] initForWritingWithMutableData:imgArrayData];
    [archiver encodeObject:imgDataArray forKey:[NSString stringWithString:model.ID]];
    [archiver finishEncoding];
    
    BOOL result = [db executeUpdate:@"INSERT INTO student (ID,name,age,imgArray) VALUES (?,?,?,?);", model.ID,model.name,model.age,imgArrayData,nil,nil];
    
    if (result) {
        NSLog(@"插入成功!");
    }else{
        NSLog(@"插入失败!");
    }
    
    
}

// 根据ID查询笔记
- (StudentModel *)selectStudentByID:(NSString *)ID{
    FMResultSet *result = [db executeQuery:@"SELECT * FROM Student where id = ?",ID];
    NSMutableArray *array = [NSMutableArray arrayWithCapacity:5];
    
    while ([result next]) {
        
        StudentModel *model = [[StudentModel alloc]init];
        model.name = [result stringForColumn:@"name"];
        model.ID = [result stringForColumn:@"ID"];
        model.age = [result stringForColumn:@"age"];
        NSData *imgArrayData = [result dataForColumn:@"imgArray"];
        
        // imgArray反归档
        NSKeyedUnarchiver * unarchiver = [[NSKeyedUnarchiver alloc] initForReadingWithData:imgArrayData];
        NSMutableArray *imgDataArray = [unarchiver decodeObjectForKey:model.ID];
        [unarchiver finishDecoding];
        
        // imgData 转 img
        NSMutableArray *imgArray = [NSMutableArray arrayWithCapacity:5];
        for (NSData *data in imgDataArray) {
            UIImage *img = [UIImage imageWithData:data];
            [imgArray addObject:img];
        }
        
        model.imgArray = imgArray;
        
        [array addObject:model];
    }
    [result close];
    
    if (array.count == 0) {
        NSLog(@"没有查到!");
        return nil;
    }
    
    return array[0];
}

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