字符串没有传递给post方法nsurlconnection

Question

我是IOS新手我使用POST方法创建了nsurlconnection我传递了参数＆＃34; str＆＃34;。在nslog str值变为null如何传递我的字符串＆＃34; str＆＃34;在post方法。

str编码：  str字符串包含branchid1，currencyid1，currencyid2取自picker视图确实选择了行。

reconfig_view()

Picker视图编码：

str = [NSString stringWithFormat:@"branch_id=%@&from_curr=%@&to_curr=%@&value=%@",branchid1,currencyid1,currencyid2,fourthstr];

按钮操作：

- (void) pickerView:(UIPickerView *)pickerView didSelectRow:(NSInteger)row inComponent:(NSInteger)component

{
    if(pickerView.tag ==2){
    txtText.text = (NSString *)[arrMsg objectAtIndex:row];
        branchid1 = (NSString *)[arrmsg1 objectAtIndex:row];

        NSLog([arrmsg1 objectAtIndex:row]);

    }else if(pickerView.tag ==1){
    currency1.text = (NSString *)[currencyname1 objectAtIndex:row];
        currencyid1 = (NSString *)[id1 objectAtIndex:row];
        NSLog([id1 objectAtIndex:row]);


    }
    else
    {
        currency2.text = (NSString *)[from_currency objectAtIndex:row];
        currencyid2 = (NSString *)[id2 objectAtIndex:row];

        NSLog(@"%@",currencyid2);
        NSLog([id2 objectAtIndex:row]);
    }

发布方法：

}

按钮操作：

-(void) sendDataToServer : (NSString *) method params:(NSString *)str{


    NSData *postData = [str dataUsingEncoding:NSASCIIStringEncoding allowLossyConversion:YES];
    NSString *postLength = [NSString stringWithFormat:@"%lu", (unsigned long)[str length]];

    NSMutableURLRequest *request = [[NSMutableURLRequest alloc] initWithURL:[NSURL URLWithString:URL]];
    NSLog(@"%@",str);

    [request setHTTPMethod:@"POST"];
    [request setValue:postLength forHTTPHeaderField:@"Content-Length"];
    [request setHTTPBody:postData];

    NSURLConnection *theConnection = [NSURLConnection connectionWithRequest:request delegate:self];

    if( theConnection ){

        mutableData = [[NSMutableData alloc]init];
    }
}