objective-c - 将 C 数据类型转换为 objective-c 对象

Question

我正在使用 C api 从 mysql 数据库获取数据。我可以记录数据，所以我知道查询工作正常，但我需要将它放入字典中，Google 对此没有帮助。谁能给我一个指针、片段或链接，让我朝着正确的方向前进？

- (IBAction)dbConnect:(id)sender {


NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
MYSQL mysql;
mysql_init(&mysql);

if (!mysql_real_connect(&mysql, "10.1.1.99", "*******", "********", "oldphotoarchive", 0, NULL, 0)) {
    NSLog(@"%@", [NSString stringWithUTF8String:mysql_error(&mysql)]);
} else { 

    MYSQL_RES *result;
    MYSQL_ROW row;
    unsigned int num_fields;
    unsigned int num_rows;
    unsigned long *lengths;

    if (mysql_query(&mysql,"SELECT * FROM photorecord")) {
        // error
    } else { // query succeeded, process any data returned by it  

        result = mysql_store_result(&mysql);
        if (result)  {
            num_fields = mysql_num_fields(result);
            while ((row = mysql_fetch_row(result))) {
                lengths = mysql_fetch_lengths(result);

                lengths = mysql_fetch_lengths(result);
                for(int i = 0; i < num_fields; i++) {
                    printf("[%.*s] ", (int) lengths[i],  row[i] ? row[i] : "NULL");

                    if (row[i]) { 
                                                    //AT THIS POINT I WANT TO DO THE CONVERSION, THIS ISN'T WORKING, INCOMPATIBLE POINTER TYPE
                        NSArray* thisRow = [[NSArray alloc] initWithString: row[i]];
                    }
                }
                printf("\n");

            }


        } else  {// mysql_store_result() returned nothing; should it have?
            if (mysql_errno(&mysql)) {
                NSLog(@ "Error: %s\n", mysql_error(&mysql));
            } else if (mysql_field_count(&mysql) == 0) {
                // query does not return data
                // (it was not a SELECT)
                num_rows = mysql_affected_rows(&mysql);
            }
        }

    }

}

[pool release];
}

这是修改后的代码，以防其他人遇到同样的情况。欢迎批评指正:

#import "AppController.h"

#include "mysql.h"
#include "unistd.h"


@implementation AppController
- (IBAction)dbConnect:(id)sender {


NSMutableDictionary* results = [[NSMutableDictionary alloc] init];

NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
MYSQL mysql;
mysql_init(&mysql);

if (!mysql_real_connect(&mysql, "10.1.1.99", "mysqladmin", "m3r!0n", "oldphotoarchive", 0, NULL, 0)) {
    NSLog(@"%@", [NSString stringWithUTF8String:mysql_error(&mysql)]);
} else { 

    MYSQL_RES *result;
    MYSQL_ROW row;
    unsigned int num_fields;
    unsigned int num_rows;
    //unsigned long *lengths;

    NSString* itemID = [[NSString alloc] init];

    if (mysql_query(&mysql,"SELECT * FROM photorecord WHERE logNum > 10000")) {
        // error
    } else { // query succeeded, process any data returned by it  

        result = mysql_store_result(&mysql);
        if (result)  {
            num_fields = mysql_num_fields(result);

            while ((row = mysql_fetch_row(result))) {

                NSMutableDictionary* tmpDict = [[NSMutableDictionary alloc] init];

                for(int i = 0; i < num_fields; i++) {
                    if (row[i]) { 
                        char* cString = row[i];
                        NSString* dataString  = [NSString stringWithCString:cString encoding:NSUTF8StringEncoding];
                        if ([dataString isNotEqualTo: @"NULL"]) { 
                            //NSLog(@"%@", dataString);

                            if (i==0) { 
                                itemID = dataString;
                            }

                            [tmpDict setObject: dataString forKey: [NSString stringWithFormat: @"item_%i", i] ];
                        }
                    }
                }

                [results setObject:tmpDict forKey:itemID];
                NSLog(@"%@", results);

            }

        } else  {// mysql_store_result() returned nothing; should it have?
            if (mysql_errno(&mysql)) {
                NSLog(@ "Error: %s\n", mysql_error(&mysql));
            } else if (mysql_field_count(&mysql) == 0) {
                // query does not return data
                // (it was not a SELECT)
                num_rows = mysql_affected_rows(&mysql);
            }
        }

    }

}


[pool release];

}
@end

为了让 MySQL 在您的项目中工作，您必须进行一些设置:

1. 将两个框架文件 libmysqlclient.a 和 libmysqlclient_r.a(应该在/usr/local/mysql/lib 中)复制到您的项目中(将它们放在框架组/文件夹中)。当您将内容复制到项目中时，包括所有子文件夹或任何消息。

2. 展开目标，右键单击然后选择添加 -> 添加新构建阶段 -> 新建复制文件构建阶段。将目标更改为框架。这会将这两个框架放入项目的构建中。

3. 将/usr/local/mysql/include 文件夹复制到您的项目中。这些是 MySQL 头文件。

Answer 1

NSArray 没有“initWithString”方法。 .

可能你想要的是这样的……

NSString *s = [NSString alloc] initWithBytes: row[i] length: strlen(row[i]) encoding: DefaultCstring]