在另一个类objective-c中保存一个类的实例

Posted 2023-03-08

【中文标题】在另一个类objective-c中保存一个类的实例

【英文标题】：Save instance of an class in another class objective-c

【发布时间】：2018-03-30 10:48:45

【问题描述】：

在课堂上我正在与fmdb建立数据库连接

类似（伪代码）：

// someClass.m
- (void)sameDatabase:(NSString *)database
    if (database is the same as before)
    
        // call method and access reference previously saved in class (someClass) in else statement
     else 
        ...
        [database open]; //FMDB
        // save reference to database in class (someClass)
        // call method and access reference saved in class (someClass)
    

如何在课堂上保存对database 的引用？

【参考方案1】：

将引用存储在数据成员中。在 Objective-C 中，这将类似于以下内容。我使用SomeClass 的类名并假设FMDatabase 有一个name 成员。

// someClass.m

@interface SomeClass () // In the .m file, this is for defining private members

    FMDatabase* _database; // Convention is to have private data start with _

@end

@implementation SomeClass

- (void)sameDatabase:(NSString *)database 
    if ([_database.databasePath isEqualToString:database]) 
        // call method and access reference previously saved in class (someClass) in else statement
     else 
        ...
        // I can't say what this line should be, so I just used your code.
        // It would depend on the database you are using.
       _database = [FMDatabase databaseWithPath: database];
       [_database open];
    


@end

【讨论】：

嗯，不确定。那行_database = [database open] 给了我Implicit conversion of 'BOOL' (aka 'bool') to 'FMDatabase *' is disallowed with ARC 我将@interface 更改为@interface SomeClass () FMDatabase* _database; @end

我查找了 FMDatabase 的 api，所以我认为现在的代码更好。

感谢您的帮助