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Obj-c - 如果 tableview 部分为空，应用程序崩溃？

[英]Obj-c - App crashing if tableview section is empty?

 原文  2021-02-10 22:19:10  0   1    ios/ objective-c/ uitableview

问题描述

我正在使用下面的代码按字母顺序组织我的 tableView。 过滤器工作正常，但是如果其中一个部分不包含任何结果（即字母“A”没有返回任何内容），它会导致我的应用程序崩溃，因为 tableView 正在尝试使用不包含的数据填充单元格那里。 知道如何防止这种情况吗？

视图控制器.m

- (void)viewDidLoad {
                [super viewDidLoad];
                
 self.clientSections = [NSArray arrayWithObjects:@"#", @"a", @"b", @"c", @"d", @"e", @"f", @"g", @"h", @"i", @"j", @"k", @"l", @"m", @"n", @"o", @"p", @"q", @"r", @"s", @"t", @"u", @"v", @"w", @"x", @"y", @"z", nil];
    
    
 NSMutableDictionary *viewParams1 = [NSMutableDictionary new];
        [viewParams1 setValue:@"cdata" forKey:@"view_name"];
        [DIOSView viewGet:viewParams1 success:^(AFHTTPRequestOperation *operation, id responseObject) {
            
            self.clients = [responseObject mutableCopy];
          
            
NSSortDescriptor *sort = [NSSortDescriptor sortDescriptorWithKey:@"last name" ascending:YES];
    
self.clientsAZ = [self.clients sortedArrayUsingDescriptors:@[sort]];
            
    
               } failure:^(AFHTTPRequestOperation *operation, NSError *error) {
            NSLog(@"Failure: %@", [error localizedDescription]);
        }];
        
            
           -(NSInteger)numberOfSectionsInTableView:(UITableView *)tableView {
    
        
        return [self.clientSections count];
        
    }
    
    - (NSArray *)sectionIndexTitlesForTableView:(UITableView *)tableView {
          return self.clientSections;
    }
    
    - (NSString *)tableView:(UITableView *)tableView titleForHeaderInSection:(NSInteger)section {
     
        return [self.clientSections objectAtIndex:section];
      
        
    }
            
            
-(NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
            
                
 self.finalfiltered = [self.clientsAZ  filteredArrayUsingPredicate:[NSPredicate predicateWithFormat:@"(%K beginswith[cd] %@)", @"last name", [self.clientSections objectAtIndex:section]]];
                    
                
                    return [self.finalfiltered count];
                 
            }
            
    
            -(UITableViewCell *)tableView:(UITableView*)tableView cellForRowAtIndexPath:(nonnull NSIndexPath *)indexPath {
                
               
                    static NSString *ClientTableIdentifier = @"ClientTableViewCell";
                    
                    ClientTableViewCell *cell = (ClientTableViewCell *)[self.tableView dequeueReusableCellWithIdentifier:ClientTableIdentifier];
                    
                    if (cell == nil)
                    {
                        NSArray *nib = [[NSBundle mainBundle] loadNibNamed:@"ClientTableViewCell" owner:self options:nil];
                        cell = [nib objectAtIndex:0];
                        
                    }
                   
                
                NSString *photo = [self.finalfiltered valueForKey:@"client photo"][indexPath.row];
                 
                NSString *first = [self.finalfiltered valueForKey:@"first name"][indexPath.row];
                   
                NSString *last = [self.finalfiltered valueForKey:@"last name"][indexPath.row];
                  
                NSString *telephone = [self.finalfiltered valueForKey:@"phone"][indexPath.row];
                  
                NSString *fullName = [NSString stringWithFormat:@"%@ %@", first, last];
              
                cell.clientName.text = fullName;
                cell.subtext.text = telephone;
                    
                NSURL *imageUrl = [NSURL URLWithString:photo];
                NSLog(@"The photo url is %@", photo);
                [cell.clientPhoto setImageWithURL:imageUrl];
                    
                    return cell;
                    
                    
                    }
                    
                    
              }

编辑：这是我记录 self.finalfiltered 时返回的内容。 注意，我是按姓氏排序的。 顺序似乎是正确的。

2021-02-10 16:53:34.905601-0800 [1784:532468] THE FINAL FILTER (
)
2021-02-10 16:53:34.905846-0800 -[1784:532468] THE FINAL FILTER (
)
2021-02-10 16:53:34.906076-0800 -[1784:532468] THE FINAL FILTER (
)
2021-02-10 16:53:34.906335-0800 -[1784:532468] THE FINAL FILTER (
)
2021-02-10 16:53:34.906566-0800 -[1784:532468] THE FINAL FILTER (
)
2021-02-10 16:53:34.906772-0800 -[1784:532468] THE FINAL FILTER (
)
2021-02-10 16:53:34.907025-0800 -[1784:532468] THE FINAL FILTER (
)
2021-02-10 16:53:34.907558-0800 -[1784:532468] THE FINAL FILTER (
)
2021-02-10 16:53:34.907772-0800 -[1784:532468] THE FINAL FILTER (
)
2021-02-10 16:53:34.908296-0800 -[1784:532468] THE FINAL FILTER (
        {
        body = none;
        city = Victoria;
        "client photo" = "/stockphotos/person5.png";
        country = Canada;
        email = "thomas.ingram@outlook.com";
        "first name" = Thomas;
        "last name" = Ingram;
        "mailing address" = "502 Catherine Street";
        "mailing address 2" = "Apt 403";
        nid = 127;
        "node_title" = "Thomas Ingram";
        notes = "test notes";
        phone = "250-998-0389";
        scheduleddate = "Feb 8 2021 1:00 PM";
        scheduledtime = none;

        "state or province" = BC;
        "zip code" = "V9A 3T3";
    }
)
2021-02-10 16:53:34.908833-0800 -[1784:532468] THE FINAL FILTER (
        {
        body = none;
        city = Toronto;
        "client photo" = "/stockphotos/person2.png";
        country = Canada;
        email = "andrea@gmail.com";
        "first name" = Andrea;
        "last name" = Johnson;
        "mailing address" = "227 Willow Avenue";
        "mailing address 2" = "Unit 2034";
        nid = 124;
        "node_title" = "Andrea Johnson";
        notes = "test notes";
        phone = "416-223-2397";
        scheduleddate = "Feb 8 2021 07:00 PM";
        scheduledtime = "5:45 PM";
        "state or province" = ON;
        "zip code" = "M5M 1W4";
    }
)
2021-02-10 16:53:34.909541-0800 -[1784:532468] THE FINAL FILTER (
        {
        body = none;
        city = Burnaby;
        "client photo" = "/sites/default/files/stored/1612926759.jpg";
        country = Canada;
        email = email@email.com;
        "first name" = Cody;
        "last name" = Lin;
        "mailing address" = "4036 Pandora Street";
        "mailing address 2" = "-";
        nid = 171;
        "node_title" = "Cody Lin”;
        notes = "test notes”;
        phone = "604-250-7422";
        scheduleddate = none;
        scheduledtime = none;
        "state or province" = BC;
        "zip code" = V5C2A9;
    }
)
2021-02-10 16:53:34.910439-0800 -[1784:532468] THE FINAL FILTER (
        {
        body = none;
        city = "New York City";
        "client photo" = "/stockphotos/person4.png";
        country = US;
        email = "mlevy39@gmail.com";
        "first name" = Michael;
        "last name" = Levy;
        "mailing address" = "22 Lexington Avenue";
        "mailing address 2" = "Apt 102";
        nid = 126;
        "node_title" = "Michael Levy";
        notes = "test notes";
        phone = "212-983-0029";
        scheduleddate = "Feb 10 2021 1:00 PM";
        scheduledtime = none;
        "state or province" = NY;
        "zip code" = 90020;
    },
        {
        body = none;
        city = London;
        "client photo" = "/stockphotos/person1.png";
        country = Canada;
        email = "janinejlohr@gmail.com";
        "first name" = Janine;
        "last name" = Monroe;
        "mailing address" = "909 Fake Street";
        "mailing address 2" = "Unit 4103";
        nid = 123;
        "node_title" = "Janine Monroe";
        notes = "test notes";
        phone = "778-028-2938";
        scheduleddate = "Feb 14 2021 7:37 PM, Feb 17 2021 9:00 AM";
        scheduledtime = none;
        "state or province" = BC;
        "zip code" = "V6E 4V2";
    }
)
2021-02-10 16:53:34.911207-0800 -[1784:532468] THE FINAL FILTER (
)
2021-02-10 16:53:34.911423-0800 -[1784:532468] THE FINAL FILTER (
)
2021-02-10 16:53:34.911630-0800 -[1784:532468] THE FINAL FILTER (
)
2021-02-10 16:53:34.911834-0800 -[1784:532468] THE FINAL FILTER (
)
2021-02-10 16:53:34.912033-0800 -[1784:532468] THE FINAL FILTER (
)
2021-02-10 16:53:34.912233-0800 -[1784:532468] THE FINAL FILTER (
)
2021-02-10 16:53:34.912431-0800 -[1784:532468] THE FINAL FILTER (
)
2021-02-10 16:53:34.913457-0800 -[1784:532468] THE FINAL FILTER (
)
2021-02-10 16:53:34.913671-0800 -[1784:532468] THE FINAL FILTER (
)
2021-02-10 16:53:34.913931-0800 -[1784:532468] THE FINAL FILTER (
)
2021-02-10 16:53:34.914378-0800 -[1784:532468] THE FINAL FILTER (
        {
        body = none;
        city = Vancouver;
        "client photo" = "/stockphotos/person3.png";
        country = Canada;
        email = "cali.wright@gmail.com";
        "first name" = Cali;
        "last name" = Wright;
        "mailing address" = "667 Fake Street";
        "mailing address 2" = "Apt 4102";
        nid = 125;
        "node_title" = "Cali Wright";
        notes = "test notes”;
        phone = "778-867-7184";
        scheduleddate = none;
        scheduledtime = none;
        "state or province" = BC;
        "zip code" = none;
    }
)
2021-02-10 16:53:34.914652-0800 -[1784:532468] THE FINAL FILTER (
)
2021-02-10 16:53:34.914868-0800 -[1784:532468] THE FINAL FILTER (
)

发生的崩溃是：

Terminating app due to uncaught exception 'NSRangeException', reason: '*** -[__NSArray0 objectAtIndex:]: index 0 beyond bounds for empty NSArray'

最后，在代码中，它似乎在这一行之前崩溃了：

 NSString *photo = [self.finalfiltered valueForKey:@"client photo"][indexPath.row];

1 个解决方案

解决方案1
 1 已采纳  2021-02-11 07:55:06

您的方法是始终为表格视图中的部分数返回27 ，对应于数字和字母 AZ。 但是， UITableView不能有 0 行的部分。 这意味着当您的数据不包含以“b”开头的姓氏时，您会遇到问题，例如； 您为第 1 部分返回 0，但这是不允许的。 tableview 仍然为空部分请求第 0 行，并且您得到一个数组边界异常。

为了回答的目的，我稍微简化了您的单元格显示代码，因为我不想完全填充所有数据字段并设置自定义单元格（您应该真正使用 object 来封装您的数据 model 而不是还有一本字典）。

大部分工作在splitClients方法中完成 - 这将为每个部分和部分标题创建适当的 arrays。 在这段代码中，我确保数据是按排序顺序创建的，但是您可以像在代码中那样对数据进行排序。

通过创建正确的 arrays，您可以看到numberOfSections和numberOfRowsInSection简单得多 - 您希望这些函数以及cellForRowAt高效，因为它们将在表格视图滚动时被多次调用。

另一种注意方法是sectionForSectionIndexTitle - 由于可能不会填充所有索引部分，因此此 function 用于返回最近填充的部分，因此如果您 select “b”并且没有“b”，它将滚动到“C”。

@interface ViewController ()

@property NSArray<NSDictionary *> *clients;
@property NSArray<NSArray *> *sectionClients;
@property NSArray<NSString *> *sectionLetters;
@property NSArray<NSString *> *sectionHeaders;
@property IBOutlet UITableView *tableView;
@end

@implementation ViewController


- (void)viewDidLoad {
    [super viewDidLoad];
    self.sectionLetters = [NSArray arrayWithObjects:@"#", @"a", @"b", @"c", @"d", @"e", @"f", @"g", @"h", @"i", @"j", @"k", @"l", @"m", @"n", @"o", @"p", @"q", @"r", @"s", @"t", @"u", @"v", @"w", @"x", @"y", @"z", nil];
    // Do any additional setup after loading the view.
    
    NSMutableArray *clients = [NSMutableArray new];
    [clients addObject:[self clientWithFirstname:@"Andrew" lastName:@"67Anderson"]];
    [clients addObject:[self clientWithFirstname:@"Andrew" lastName:@"Anderson"]];
    [clients addObject:[self clientWithFirstname:@"Zaphod" lastName:@"Beeblebrox"]];
    [clients addObject:[self clientWithFirstname:@"Bob" lastName:@"Carlson"]];
    [clients addObject:[self clientWithFirstname:@"David" lastName:@"Carlson"]];
    [clients addObject:[self clientWithFirstname:@"Anthony" lastName:@"Edwards"]];
    [clients addObject:[self clientWithFirstname:@"Griff" lastName:@"Jones"]];
    [clients addObject:[self clientWithFirstname:@"Sara" lastName:@"Kelly"]];
    [clients addObject:[self clientWithFirstname:@"Mabel" lastName:@"Maloney"]];
    [clients addObject:[self clientWithFirstname:@"Horatio" lastName:@"Newton"]];
    [clients addObject:[self clientWithFirstname:@"Josie" lastName:@"Peters"]];
    [clients addObject:[self clientWithFirstname:@"Mel" lastName:@"Smith"]];
    [clients addObject:[self clientWithFirstname:@"Michael" lastName:@"Taylor"]];
    [clients addObject:[self clientWithFirstname:@"Mary" lastName:@"Zax"]];
    
    self.clients = [clients copy];
    
    [self splitClients];
    NSLog(@"Done splitting");
}

-(NSDictionary *)clientWithFirstname:(NSString *)firstName lastName:(NSString *)lastName {
    NSMutableDictionary *dict = [NSMutableDictionary new];
    dict[@"first name"] = firstName;
    dict[@"last name"] = lastName;
    return dict;
}

-(void)splitClients {
    
    NSMutableArray *sectionClients = [NSMutableArray new];
    NSMutableArray *sectionHeaders = [NSMutableArray new];
    
    // Look for last names that start with a digit using a regex

    NSArray *digitClients = [self.clients filteredArrayUsingPredicate:[NSPredicate predicateWithFormat:@"(%K MATCHES %@)",@"last name",@"[0-9].*" ]];
    
    // Add a section for digit names if any were found

    if ([digitClients count] > 0) {
        [sectionClients addObject:digitClients];
        [sectionHeaders addObject:@"#"];
    }
    
    // Now check for names starting with each letter of the alphabet

    for (NSString *letter in self.sectionLetters) {
        
        NSArray *letterArray = [self.clients filteredArrayUsingPredicate:[NSPredicate predicateWithFormat:@"(%K beginswith[cd] %@)", @"last name",letter]];

        // If any matching names were found, add them as a new section

        if ([letterArray count] >0) {
            [sectionClients addObject:letterArray];
            [sectionHeaders addObject:letter];
        }
    }
    
    self.sectionClients = [sectionClients copy];
    self.sectionHeaders = [sectionHeaders copy];
}

-(NSInteger)numberOfSectionsInTableView:(UITableView *)tableView {
    return [self.sectionClients count];
}

- (NSArray *)sectionIndexTitlesForTableView:(UITableView *)tableView {
    return self.sectionLetters;
}

- (NSString *)tableView:(UITableView *)tableView titleForHeaderInSection:(NSInteger)section {
    
    return self.sectionHeaders[section];
 
}


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

- (NSInteger)tableView:(UITableView *)tableView
sectionForSectionIndexTitle:(NSString *)title
               atIndex:(NSInteger)index {
    
    NSInteger targetSection = 0;
    
    for (NSString *letter in self.sectionHeaders) {
        NSComparisonResult result = [title compare:letter];
        // If the section index is >= the target index, break and exit
        if (result == NSOrderedAscending || result == NSOrderedSame) {
            break;
        }
        // Otherwise increment the section number
        targetSection++;
    }
    
    return targetSection;
}


-(UITableViewCell *)tableView:(UITableView*)tableView cellForRowAtIndexPath:(nonnull NSIndexPath *)indexPath {
    
    NSDictionary *client = self.sectionClients[indexPath.section][indexPath.row];
    
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:@"Cell" forIndexPath:indexPath];
    
    cell.textLabel.text = [NSString stringWithFormat:@"%@ %@", client[@"first name"], client[@"last name"]];
    
    return cell;
    
}

@end

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