iPhone 应用程序崩溃 - viewDidLoad

Question

当我向主视图 Controller 中的 viewDidLoad 添加方法时，我的 iPhone 应用程序崩溃了:

#import "dbQuestionGetterViewController.h"
#import "dbConnector.h";

@implementation dbQuestionGetterViewController
@synthesize questions;

-(void)viewDidLoad{
    //code to initialise view
    NSDictionary* arr = [dbConnector getQuestions:2 from:@"http://dev.speechlink.co.uk/David/get_questions.php"];
    questions = arr;
    [arr release];  
    [super viewDidLoad];
}

我正在从 dbConnector 类调用静态方法，但它在加载之前就崩溃了..

dbConnector中的方法:

//method to 
+(NSDictionary*)getQuestions:(NSInteger)sectionId from: (NSString*) url{
    //connect to database given by url
    //NSError        *error = nil;
    //NSURLResponse  *response = nil;
    NSMutableString* myRequestString = [[NSMutableString string]initWithFormat:@"section=%@", sectionId];
    NSData *myRequestData = [NSData dataWithBytes: [myRequestString UTF8String] length: [myRequestString length]];
    NSMutableURLRequest *request = [[NSMutableURLRequest alloc] initWithURL: [NSURL URLWithString: url]]; 
    [request setValue:@"application/x-www-form-urlencoded" forHTTPHeaderField:@"content-type"];
    [request setHTTPMethod: @"POST"];
    //post section 
    [request setHTTPBody: myRequestData];

    //store them in the dictionary
    NSData *data = [NSData dataWithContentsOfURL:[NSURL URLWithString:url]];
    NSString *json = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
    NSDictionary *questions = [json objectFromJSONString];
    [json release];

    [request release];
    return [questions autorelease];
}

我做错了什么？

Answer 1

首先，您没有对这段代码执行任何操作:

NSMutableString* myRequestString = [[NSMutableString string]initWithFormat:@"section=%@", sectionId];
NSData *myRequestData = [NSData dataWithBytes: [myRequestString UTF8String] length: [myRequestString length]];
NSMutableURLRequest *request = [[NSMutableURLRequest alloc] initWithURL: [NSURL URLWithString: url]]; 
[request setValue:@"application/x-www-form-urlencoded" forHTTPHeaderField:@"content-type"];
[request setHTTPMethod: @"POST"];
//post section 
[request setHTTPBody: myRequestData];

删除它。

其次，问题已经自动发布。

NSDictionary *questions = [json objectFromJSONString]; // < autoreleased

因此，只需执行 return questions; 就可以了。

这也意味着您在任何情况下都不应该释放此返回值。因此，摆脱这个:

[arr release];