如何解决Obj-c - 如果 tableview 部分为空，应用程序会崩溃吗？
我正在使用以下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 试图用不是的数据填充单元格那里。知道如何防止这种情况吗？
ViewController.m
this编辑： 这是我登录 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。
- (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;
}
}
发生的崩溃是：
2021-02-10 16:53:34.905601-0800 [1784:532468] THE FINAL FILTER (
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2021-02-10 16:53:34.905846-0800 -[1784:532468] THE FINAL FILTER (
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2021-02-10 16:53:34.906076-0800 -[1784:532468] THE FINAL FILTER (
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2021-02-10 16:53:34.906335-0800 -[1784:532468] THE FINAL FILTER (
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2021-02-10 16:53:34.906566-0800 -[1784:532468] THE FINAL FILTER (
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2021-02-10 16:53:34.907558-0800 -[1784:532468] THE FINAL FILTER (
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2021-02-10 16:53:34.907772-0800 -[1784:532468] THE FINAL FILTER (
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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 (
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2021-02-10 16:53:34.913671-0800 -[1784:532468] THE FINAL FILTER (
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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 (
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2021-02-10 16:53:34.914868-0800 -[1784:532468] THE FINAL FILTER (
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Terminating app due to uncaught exception 'NSRangeException',reason: '*** -[__NSArray0 objectAtIndex:]: index 0 beyond bounds for empty NSArray'
解决方法
您的方法是始终返回 27 作为 tableview 中部分的数量，对应于数字和字母 A-Z。但是，UITableView 不能有包含 0 行的部分。例如，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；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，并且您会收到数组边界异常。
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（您真的应该使用一个对象来封装您的数据模型而不是字典）。
大部分工作是在方法 splitClients 中完成的 - 这会为每个部分和部分标题创建适当的数组。在这段代码中，我确保数据是按排序顺序创建的，但您可以像在代码中那样对数据进行排序。
通过创建正确的数组，您可以看到 numberOfSections 和 numberOfRowsInSection 是多么简单 - 您希望这些函数以及 cellForRowAt 高效，因为它们将被多次调用为表格视图滚动。
注意的另一种方法是sectionForSectionIndexTitle - 由于并非所有索引部分都可能被填充，此函数用于返回最近的填充部分，因此如果您选择“b”并且没有“b” "s，它会滚动到 "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] %@)",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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