Question

我写了以下代码：

NSData *response = [NSURLConnection sendSynchronousRequest:request returningResponse:nil error:nil];
NSString *json_string = [[NSString alloc] initWithData:response encoding:NSUTF8StringEncoding];
NSDictionary *reportDic = [jsonparser objectWithString:json_string error:nil];
NSDictionary *reporttable = [reportDic objectForKey:@"reporttable"]; 
NSArray *rows = [reporttable objectForKey:@"rows"];


NSString *table = [[NSString alloc]initWithString:@"<table>"] ;
for (NSDictionary *row in rows)
{

    table = [table stringByAppendingString:@"<tr>"];

    NSArray *cells = [row objectForKey:@"cells"];
    for (NSString *cell in cells){
        table = [table stringByAppendingString:@"<td>"];
        table = [table stringByAppendingString:cell];
        table = [table stringByAppendingString:@"</td>"];
    }

    table = [table stringByAppendingString:@"</tr>"];
    index++;
}
table = [table stringByAppendingString:@"</table>"];
return [table autorelease];

这些行是由jsonlib解析的json响应这个字符串被返回到一个viewcontroller，将它加载到webview中，但是在完成调用它的方法后，我继续为这段代码获取exc_bad_access，我甚至不必将它加载到webview只是调用这个方法而不是使用nsstring导致调用方法完成时的错误...任何帮助将得到感谢。

- (void)viewDidLoad {

[super viewDidLoad];

AMAppDelegate *appDelegate = (AMAppDelegate*)[[UIApplication sharedApplication] delegate];
NSString * data = [appDelegate fetchTable:name psw:psw];

[webView loadHTMLString:@"this is html" baseURL:nil];
[data release];
}

有或没有释放，无关紧要

Answer 1

您的内存管理错误。

变化：

NSString *table = [[NSString alloc]initWithString:@"<table>"] ;

为：

NSString *table = [[[NSString alloc]initWithString:@"<table>"] autorelease];

然后改变：

return [table autorelease];

为：

return table;

原因是你最后自动释放的表是前一行构建的表：

table = [table stringByAppendingString:@"</table>"];

因此，您需要两次自动释放（stringByAppendingString:返回一个自动释放的实例），而根本不释放原始表。

Answer 2

如何使用NSMutableString构建表格？您当前的方法存在的一个问题是，您将不必要地充斥自动释放池。

NSMutableString *table = [NSMutableString string];

[table appendString:@"<table>"];
for (NSDictionary *row in rows)
{
    [table appendString:@"<tr>"];

    NSArray *cells = [row objectForKey:@"cells"];
    for (NSString *cell in cells){
        [table appendFormat:@"<td>%@</td>", cell];

    [table appendString:@"</tr>"];

    index++;
}
[table appendString:@"</table>"];
return table;

Answer 3

关于更新，如果您正确合并了tewhas建议，-fetchTable:psw:会返回自动释放的 NSString，因此您不应该在调用方法中发布它：

NSString *data = [appDelegate fetchTable:name psw:psw]
// ...
[data release]; // don't do that, data is autoreleased

-fetchTable:psw:应该像这样处理table：

NSString *table = [NSString stringWithString:@"<table>"] ;

// ... leave the rest as it is

return table;

请注意，您也在泄漏json_string，应该-release或-autorelease。

NSString，EXC_BAD_ACCESS和stringByAppendingString

3 个答案: