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我的程序如下:..- 但是，我想在 TitleForHeaderInSection 中按日期降序对数据进行排序，并且还想将 Header 中的日期格式化为
NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
[formatter setLocale:[[NSLocale alloc] initWithLocaleIdentifier "en_US"]];
// [formatter setDateStyle:NSDateFormatterMediumStyle];
[formatter setDateFormat"EEE, d MMM yyyy"];
NSDate *headerDate = (NSDate *)[managedObject valueForKey"dateCreated"];
NSString *headerTitle = [formatter stringFromDate:headerDate];
代码如下:
- (void)viewDidLoad {
[super viewDidLoad];
[self.navigationItem setTitle"List of Items"];
NSURL *serverURL = [NSURL URLWithString:SERVER_URL];
[[DataManager sharedInstance] loadData:serverURL withCompletion:^(NSArray *itemListArray, NSError *error) {
if (error != nil) {
UIAlertView *errorAlertView = [[UIAlertView alloc] initWithTitle"Server Error" message"Unable to fetch Data from Server" delegate:nil cancelButtonTitle"Ok" otherButtonTitles:nil, nil];
[errorAlertView show];
}
else {
fetchData = [self convertSectionTableData:itemListArray keyString"date"];
[self.listTableView reloadData];
}
}];
[self.listTableView reloadData];}
- (NSMutableDictionary *)convertSectionTableData NSArray *)convertDataSet keyStringNSString *)keyString {
NSMutableDictionary *outputData = [NSMutableDictionary dictionary];
NSMutableArray *temp = [NSMutableArray array];
NSString *key = NULL;
for (NSDictionary *dic in convertDataSet) {
if (key == NULL) {
key = [dic objectForKey:keyString];
} else if (key != [dic objectForKey:keyString]) {
[outputData setValue:temp forKey:key];
temp = [NSMutableArray array];
key = [dic objectForKey:keyString];
}
if ([[dic objectForKey:keyString] isEqualToString: key]) {
[temp addObject:dic];
}
if (dic == [convertDataSet lastObject]) {
[outputData setValue:temp forKey:key];
}
}
return outputData;}
- (NSInteger)numberOfSectionsInTableViewUITableView *)tableView {
return [fetchData count];}
-(NSInteger)tableViewUITableView *)tableView numberOfRowsInSectionNSInteger)section {
return [[fetchData allValues][section] count];}
-(UITableViewCell *)tableViewUITableView *)tableView cellForRowAtIndexPathNSIndexPath *)indexPath {
static NSString *cellIdentifier = @"CustomListTableCell";
CustomListTableCell *cell = (CustomListTableCell *)[tableView dequeueReusableCellWithIdentifier:cellIdentifier];
int section = (int)indexPath.section;
int row = (int)indexPath.row;
NSDictionary *data = [[fetchData allValues][section] objectAtIndex:row];
cell.homeLabel.text = [data objectForKey"home"];
return cell;}
- (NSString *)tableViewUITableView *)tableView titleForHeaderInSectionNSInteger)section {
return [fetchData allKeys][section];}
@end
Best Answer-推荐答案
基本思想是字典是无序的，因此您需要某种方法以正确的顺序检索它们。我可能会建议构建字典键的排序数组。
// build dictionary of objects, keyed by date
NSMutableDictionary *objectsForDates = ...
// build sorted array of dates in descending order
NSArray *dates = [[objectsForDates allKeys] sortedArrayUsingComparator:^NSComparisonResult(id _Nonnull obj1, id _Nonnull obj2) {
return [obj2 compare bj1];
}];
然后您可以使用此 dates 对象来表示表格 View 的“部分”，然后使用它来知道要返回字典中的哪个条目:
- (NSInteger)numberOfSectionsInTableViewUITableView *)tableView {
return [self.dates count];
}
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
return [self.objectsForDates[self.dates[section]] count];
}
- (NSString *)tableView:(UITableView *)tableView titleForHeaderInSection:(NSInteger)section {
return [self.formatter stringFromDate:self.dates[section]];
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier"Cell" forIndexPath:indexPath];
Location *object = self.objectsForDates[self.dates[indexPath.section]][indexPath.row];
cell.textLabel.text = object.home;
return cell;
}
注意，我建议对您的代码进行一些不相关的更改:
我建议对 JSON 的内容使用自定义对象类型。这提供了比简单的 NSDictionary 更强的类型。
我还要确保类型更自然地键入(例如，id 看起来应该是 NSInteger；date 看起来应该是 NSDate)。
我还要给这个自定义类型一个 initWithDictionary 初始化器，以简化解析代码。 构建以日期为键的字典的逻辑(您的 convertSectionTableData)可以简化一点。 您的 UI 日期格式化程序不应使用 en_US 的 locale。解析 JSON 的格式化程序应该(或者更准确地说，它应该使用 en_US_POSIX)，但是在 UI 中呈现格式时，应该使用用户自己的语言环境。
您的 UI 日期格式化程序也不应该使用固定的 dateFormat 字符串。使用预先存在的 dateStyle 之一，或者如果您必须使用 dateFormat，则使用 dateFormatFromTemplate 构建本地化版本。
不管怎样，把它们放在一起，你会得到类似的东西:
@interface Location : NSObject
@property (nonatomic) NSInteger identifier;
@property (nonatomic, copy) NSString *home;
@property (nonatomic, strong) NSDate *date;
- (instancetype)initWithDictionary:(NSDictionary *)dictionary;
@end
@implementation Location
- (instancetype)initWithDictionary:(NSDictionary *)dictionary {
self = [super init];
if (self) {
self.identifier = [dictionary[@"id"] integerValue];
self.home = dictionary[@"home"];
[self setDateFromString:dictionary[@"date"]];
}
return self;
}
- (void)setDateFromString:(NSString *)string {
static NSDateFormatter *formatter;
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
formatter = [[NSDateFormatter alloc] init];
formatter.locale = [NSLocale localeWithLocaleIdentifier:@"en_US_POSIX"];
formatter.timeZone = [NSTimeZone timeZoneForSecondsFromGMT:0];
formatter.dateFormat = @"yyyy-MM-dd";
});
self.date = [formatter dateFromString:string];
}
@end
和
@interface ViewController ()
@property (nonatomic, strong) NSMutableDictionary *objectsForDates;
@property (nonatomic, strong) NSArray *dates;
@property (nonatomic, strong) NSDateFormatter *formatter;
@end
@implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
// set formatter for output
self.formatter = [[NSDateFormatter alloc] init];
[self.formatter setDateFormat:[NSDateFormatter dateFormatFromTemplate:@"EEEdMMMyyyy" options:0 locale:[NSLocale currentLocale]]];
self.formatter.timeZone = [NSTimeZone timeZoneForSecondsFromGMT:0];
// perform request
NSURL *url = [NSURL URLWithString:@"http://borindatabase.000webhostapp.com/jsonData.php"];
[[[NSURLSession sharedSession] dataTaskWithURL:url completionHandler:^(NSData * _Nullable data, NSURLResponse * _Nullable response, NSError * _Nullable error) {
if (error || !data) {
NSLog(@"networkError: %@", error);
return;
}
NSError *parseError;
NSArray *values = [NSJSONSerialization JSONObjectWithData:data options:0 error:&parseError];
if (![values isKindOfClass:[NSArray class]]) {
NSLog(@"parseError: %@", parseError);
}
// build dictionary of objects, keyed by date
NSMutableDictionary *objectsForDates = [[NSMutableDictionary alloc] init];
for (NSDictionary *value in values) {
Location *object = [[Location alloc] initWithDictionary:value];
NSMutableArray *objects = objectsForDates[object.date];
if (!objects) {
objects = [[NSMutableArray alloc] init];
objectsForDates[object.date] = objects;
}
[objects addObjectbject];
}
// build sorted array of dates in descending order
NSArray *dates = [[objectsForDates allKeys] sortedArrayUsingComparator:^NSComparisonResult(id _Nonnull obj1, id _Nonnull obj2) {
return [obj2 comparebj1];
}];
// now update UI
dispatch_async(dispatch_get_main_queue(), ^{
self.objectsForDates = objectsForDates;
self.dates = dates;
[self.tableView reloadData];
});
}] resume];
}
- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView {
return [self.dates count];
}
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
return [self.objectsForDates[self.dates[section]] count];
}
- (NSString *)tableView:(UITableView *)tableView titleForHeaderInSection:(NSInteger)section {
return [self.formatter stringFromDate:self.dates[section]];
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:@"Cell" forIndexPath:indexPath];
Location *object = self.objectsForDates[self.dates[indexPath.section]][indexPath.row];
cell.textLabel.text = object.home;
return cell;
}
@end
关于ios - 如何在 TitleForHeaderInSection 上对日期进行排序，我们在Stack Overflow上找到一个类似的问题：
https://stackoverflow.com/questions/44877601/
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