為什么要使用FMDatabaseQueue

• FMDatabase這個類, 他不是線程安全的, 如果在多個線程中同時使用一個FMDataBase對象來存取數(shù)據(jù)的話, 有可能會發(fā)生數(shù)據(jù)錯亂
• 因此為了保證線程安全, 要使用FMDatabaseQueue這個類來操作數(shù)據(jù)
• FMDatabaseQueue這個類, 還提供了在一個SQL字符串中, 同時編寫多個代碼的方法, 因此使用起來十分的效率

簡單的代碼實現(xiàn)

 #import "DataBaseTool.h"
 #import "FMDatabase.h"
 #import "FMDatabaseQueue.h"
 
 static DataBaseTool *_instance;
 
 @interface DataBaseTool ()
 @property (nonatomic, strong) FMDatabaseQueue *queue;
 @end
 
 @implementation DataBaseTool
 
 + (instancetype)shareInstance {
     static dispatch_once_t onceToken;
     dispatch_once(&onceToken, ^{
         _instance = [[self alloc] init];
     });
     
     return _instance;
 }
 
 // 懶加載數(shù)據(jù)庫隊列
 - (FMDatabaseQueue *)queue {
     if (_queue == nil) {
         _queue = [FMDatabaseQueue databaseQueueWithPath:@"/Users/fanghe/Desktop/數(shù)據(jù)庫/demo.sqlite"];
     }
     
     return _queue;
 }
 
 // 創(chuàng)建表
 - (void)createTableWithSQL:(NSString *)sql {
     
     [self.queue inDatabase:^(FMDatabase *db) {
         BOOL result = [db executeUpdate:sql withArgumentsInArray:nil];
         if (result) {
             NSLog(@"創(chuàng)建表格成功");
         } else {
             NSLog(@"創(chuàng)建表格失敗");
         }
     }];
 }
 
 // 刪除表格
 - (void)dropTableWithSQL:(NSString *)sql {
     
     [self.queue inDatabase:^(FMDatabase *db) {
         BOOL result = [db executeUpdate:sql withArgumentsInArray:nil];
         if (result) {
             NSLog(@"刪除表格成功");
         } else {
             NSLog(@"刪除表格失敗");
         }
     }];
 }
 
 // 插入數(shù)據(jù)
 - (void)insertDataWithSQL:(NSString *)sql {
     
     [self.queue inDatabase:^(FMDatabase *db) {
         BOOL result = [db executeUpdate:sql withArgumentsInArray:nil];
         if (result) {
             NSLog(@"插入數(shù)據(jù)成功");
         } else {
             NSLog(@"插入數(shù)據(jù)失敗");
         }
     }];
 }
 
 // 查詢所有數(shù)據(jù)
 - (void)queryAll {
     
     [self.queue inDatabase:^(FMDatabase *db) {
         NSString *sql = @"select * from T_human";
         
         FMResultSet *resultSet = [db executeQuery:sql withArgumentsInArray:nil];
         
         while (resultSet.next) {
             NSString *name = [resultSet stringForColumn:@"name"];
             int age = [resultSet intForColumn:@"age"];
             double height = [resultSet doubleForColumn:@"height"];
             
             NSLog(@"%@, %i, %lf", name, age, height);
         }
     }];
 }
 
 // 執(zhí)行多條語句
 - (void)excuteStaments {
     
     NSString *sql = @"insert into T_human(name, age, height) values('wangwu', 15, 170);insert into T_human(name, age, height) values('zhaoliu', 13, 160);";
     
     [self.queue inDatabase:^(FMDatabase *db) {
         BOOL result = [db executeStatements:sql];
         if (result) {
             NSLog(@"執(zhí)行多條語句成功");
         } else {
             NSLog(@"執(zhí)行多條語句失敗");
         }
     }];
 }
 
 // 開啟事務(wù)執(zhí)行語句
 - (void)transaction {
     
     [self.queue inTransaction:^(FMDatabase *db, BOOL *rollback) {
         NSString *sql = @"insert into T_human(name, age, height) values('wangwu', 15, 170);insert into T_human(name, age, height) values('zhaoliu', 13, 160);";
         NSString *sql2 = @"insert into T_human(name, age, height) values('zhaoliu', 13, 160);insert into T_human(name, age, height) values('wangwu', 15, 170);";
         
         BOOL result1 = [db executeUpdate:sql withArgumentsInArray:nil];
         BOOL result2 = [db executeUpdate:sql2 withArgumentsInArray:nil];
         
         if (result1 && result2) {
             NSLog(@"執(zhí)行成功");
         } else {
             [db rollback];
         }
     }];
 }
 
 @end