ios - 来自服务器的数据未显示在 TableView 中

Question

我有 2 个屏幕，在第一个屏幕上，当我单击一个按钮时，它应该转到第二个屏幕，从服务器获取数据并在第二个屏幕的表格 View 中显示。但是使用以下代码我无法在表格 View 中显示数据

#import "FirstTableViewController.h"

@interface FirstTableViewController ()<NSXMLParserDelegate>
@property(nonatomic,strong)NSXMLParser*xmlparse;
@property(nonatomic,strong)NSMutableString*tempstr;
@property(nonatomic,strong)NSMutableArray*arr;

@end

@implementation FirstTableViewController

- (void)viewDidLoad {
    [super viewDidLoad];

    NSMutableURLRequest*req=[[NSMutableURLRequest alloc]init];
    NSURL*url=[NSURL URLWithString:@"http://www.thomas-bayer.com/sqlrest/CUSTOMER/"];
    [req  setURL:url];
    [[[NSURLSession sharedSession]dataTaskWithRequest:req completionHandler:^(NSData * _Nullable data, NSURLResponse * _Nullable response, NSError * _Nullable error) {
        // SMXMLDocument *document = [SMXMLDocument documentWithData:data error:&error];

        NSString*str=[[NSString alloc]initWithData:data encoding:NSUTF8StringEncoding];
        _xmlparse=[[NSXMLParser alloc]initWithData:data];
        _xmlparse.delegate=self;
        [_xmlparse parse];
    }] resume];
    [_table reloadData];
}

- (void)parser:(NSXMLParser *)parser foundCharacters:(NSString *)string{
    _tempstr=[[NSMutableString alloc]initWithString:string];
}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

- (void)parser:(NSXMLParser *)parser didStartElement:(NSString *)elementName namespaceURI:(nullable NSString *)namespaceURI qualifiedName:(nullable NSString *)qName attributes:(NSDictionary<NSString *, NSString *> *)attributeDict;{
    if([elementName isEqualToString:@"CUSTOMER"]){
        self.tempstr=[[NSMutableString alloc]init];

    }
    if([elementName isEqualToString:@"CUSTOMERList"]){
        self.arr=[[NSMutableArray alloc]init];

    }

}
- (void)parser:(NSXMLParser *)parser didEndElement:(NSString *)elementName namespaceURI:(nullable NSString *)namespaceURI qualifiedName:(nullable NSString *)qName;{

    if([elementName isEqualToString:@"CUSTOMER"]){
       [_arr addObject:self.tempstr];
        self.tempstr=nil;
    }
   // NSLog(@"arr is %@",self.arr);
}
#pragma mark - Table view data source

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
    return self.arr.count;
}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:@"Cel" forIndexPath:indexPath];

    cell.textLabel.text=[self.arr objectAtIndex:indexPath.row];
    return cell;
}

@end

Answer 1

做两件事

首先

- (void)viewDidLoad {
[super viewDidLoad];

arr = [NSMutableArray array]; // initilize the memory of array 

NSMutableURLRequest*req=[[NSMutableURLRequest alloc]init];
NSURL*url=[NSURL URLWithString:@"http://www.thomas-bayer.com/sqlrest/CUSTOMER/"];
[req  setURL:url];
[[[NSURLSession sharedSession]dataTaskWithRequest:req completionHandler:^(NSData * _Nullable data, NSURLResponse * _Nullable response, NSError * _Nullable error) {
    // SMXMLDocument *document = [SMXMLDocument documentWithData:data error:&error];

    NSString*str=[[NSString alloc]initWithData:data encoding:NSUTF8StringEncoding];
    _xmlparse=[[NSXMLParser alloc]initWithData:data];
    _xmlparse.delegate=self;
    [_xmlparse parse];
}] resume];

}

第二

 - (void)parser:(NSXMLParser *)parser didEndElement:(NSString *)elementName namespaceURI:(nullable NSString *)namespaceURI qualifiedName:(nullable NSString *)qName;{

if([elementName isEqualToString:@"CUSTOMER"]){
   [_arr addObject:self.tempstr];
    self.tempstr=@"";
}

 if(arr.count >0)
 {
   dispatch_async(dispatch_get_main_queue(), ^{
             [_table reloadData];
        });

  }

 }