ARC不允许将Objective-C指针隐式转换为'const char *'？

Question

这是我的代码：

//--   check for d/b; create it if it doesn't exist
NSString *docsDir;
NSArray *dirPaths;

NSMutableArray *sqliteArray = [NSMutableArray array];
[sqliteArray addObject: @"CREATE TABLE IF NOT EXISTS SiteData (SITE_ID TEXT PRIMARY KEY NOT NULL, STA1 TEXT "
    "TBM TEST, SITE_DESC TEXT, REMARKS TEXT, LOOP_COUNT INTEGER, DATE TEXT)" ];
[sqliteArray addObject: @"INSERT INTO SiteData (SITE_ID, LOOP_COUNT) VALUES('','')"];
[sqliteArray addObject: @"CREATE TABLE Readings (SITE_ID TEXT REFERENCES SiteData, LOOP_NBR TEXT, LOOP_CLOSED BINARY, "
    "SEQ INTEGER, STA TEXT, BS TEXT, FS TEXT, DESC TEXT, SSBS TEXT, SSFS TEXT)" ];
[sqliteArray addObject: @"INSERT INTO Readings (SITE_ID, SEQ) VALUES ('','')"];
[sqliteArray addObject: @"CREATE TABLE EmailAddress (EMAIL_ADDRESS TEXT)"];
[sqliteArray addObject: @"INSERT INTO EmailAddress (EMAIL_ADDRESS) VALUES ('Enter email address here')" ];


//  get the documents directory
dirPaths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask,YES);
docsDir = [dirPaths objectAtIndex: 0];

//  build path to the d/b file
databasePath =[[NSString alloc] initWithString: [docsDir stringByAppendingPathComponent: @"r64.sdb"]];
NSFileManager *filemgr = [NSFileManager defaultManager];

if([filemgr fileExistsAtPath:databasePath] == NO)  {
    const char *dbpath = [databasePath UTF8String];
    if(sqlite3_open(dbpath, &dbLevelingData) == SQLITE_OK) {
        char *errMsg;
        int i;

        for(i = 0; i < [sqliteArray count]; i++)  {
        if(sqlite3_exec(dbLevelingData, [sqliteArray objectAtIndex:i] , NULL, NULL, &errMsg) != SQLITE_OK)  
            status.text = @"Failed to create table";
        }

        sqlite3_close(dbLevelingData);
    }
    else 
        status.text = @"Failed to open/create database";
}

在“if（sqlite3_exe ...”语句中，我收到以下构建错误：

Implicit conversion of an Objective-C pointer to 'const char *' is disallowed with ARC

为什么（我没有看到任何'const'char）？ 以及如何解决？ （注意：我从另一个例子中复制了基本格式...... NSMutableArray不一定是可变的，如果那样会有所帮助）

Answer 1

根据这个页面 ， sqlite3_exec()定义如下：

int sqlite3_exec(sqlite3*,const char *, int (*)(void*,int,char**,char**), void *, char **);

但是，您将其调用为：

int sqlite3_exec(sqlite3 *, id, int(*)(void *)(void *, int, char**, char **), void *, char **);

因此，如果您将函数调用更改为：

sqlite3_exec(dbLevelingData, [[sqliteArray objectAtIndex:i] UTF8String], NULL, NULL, &errMsg)

您的代码应该可以正常工作（基本上，我们将您的NSString转换为const char * ）。