简介:iOS开发的持久化数据存储有4种方式:NSUserDefault和.plist、NSKeyedArchiver和NSKeyedUnarchiver、sqlite3数据库、CoreData。

sqlite3和CoreData适合存储大量数据(内容数据等),而另外两种适合存储简单数据(语言,字体,标记等简单数据存储)。

准备:这里主要介绍利用sqlite3封装的FMDatabase的数据库,(当然还有PlausibleDatabase、sqlitepersistentobjects等其他封装的库),导入需要依赖的libsqlite3.dylib包,FMDatabase已经根据工程不同情况兼容ARC和非ARC。为了只针对数据库进行讲解,直接创建一个简单工程,导入FMDatabase库。

内容:1.创建数据库

#import <UIKit/UIKit.h>
#import "FMDatabase.h"
#import "FMDatabaseQueue.h"

@interface ViewController : UIViewController{
    FMDatabase *db;
    FMDatabaseQueue *queue_db;
}

//创建数据库文件路径
- (NSString*)getPath{
    NSArray* paths =NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,NSUserDomainMask, YES) ;
    return [[paths objectAtIndex:0]stringByAppendingPathComponent:@"TEST.sqlite"] ;
}

2.数据库的建表－增－删－改操作

- (void)viewDidLoad {
    [super viewDidLoad];
    
    [self executeSql:[self createTable]];//创表
    [self executeSql:[self insertData]];//增
    [self executeSql:[self deleteData]];//删
    [self executeSql:[self setData]];//改
    //查
    [self queryData];
    //开辟多线程
    [NSThread detachNewThreadSelector:@selector(multipleThread) toTarget:self withObject:nil];
    
}

//创建数据库
-(NSString *)createTable{
    NSString *createSql = [NSString stringWithFormat:@"CREATE TABLE IF NOT EXISTS TEST(a interger,b text)"];
    return createSql;
}

//增
- (NSString *)insertData{
    NSString *insertSql= [NSString stringWithFormat:
                          @"INSERT INTO '%@' ('%@', '%@') VALUES ('%@', '%@')",
                          @"TEST", @"a", @"b", [NSNumber numberWithInt:1], @"宁波"];
    return insertSql;
}

//删
- (NSString *)deleteData{
    NSString *deleteSql = [NSString stringWithFormat: @"DELETE FROM '%@' where %@ = '%@'",
                           @"TEST", @"b", @"宁波"];
    return deleteSql;
}

//改
-(NSString *)setData{
    NSString *setSql = [NSString stringWithFormat:@"UPDATE '%@' SET '%@' = '%@' WHERE '%@' = '%@'",
                        @"TEST", @"b",  @"象山" ,@"a",  [NSNumber numberWithInt:1]];
    return setSql;
}

3.数据库的执行操作

//数据库执行操作
-(BOOL)executeSql:(NSString *)sql{
    db = [FMDatabase databaseWithPath:[self getPath]];
    BOOL success;
    if ([db open]) {
        success  = [db executeUpdate:sql];
    }else{
        NSLog(@"OPEN FAIL");
    }
    [db close];
    return success;
}

4.数据库的查询操作

//查
-(void)queryData{
    if ([db open]) {
        NSString *querySql = [NSString stringWithFormat:
                              @"SELECT * FROM %@",@"TEST"];
        FMResultSet * rs = [db executeQuery:querySql];
        while ([rs next]) {
            int a = [rs intForColumn:@"a"];
            NSString *b = [rs stringForColumn:@"b"];
            NSLog(@"a:%d  == b:%@",a,b);
        }
        
        [db close];
    }
}

5.数据库的多线程操作

若在多线程的环境下,不能在多线程中共用同一个FMDatabase进行数据访问,会造成数据混乱,多线程下不能用单例对象,这时得依靠FMDatabaseQueue。

//多线程下使用FMDatabaseQueue进行数据库操作
-(void)multipleThread{
    queue_db = [FMDatabaseQueue databaseQueueWithPath:[self getPath]];
    @autoreleasepool{
        [queue_db inDatabase:^(FMDatabase *db2) {
            [db2 executeUpdate:[self insertData]];
            [self queryData];
        }];
    }
}