viewDidLoad - 代码优化

Question

我有一些代码，但我看不出如何优化它。虽然我知道代码编写得很糟糕（我自己）。

我所拥有的是火车站名称列表。我想要做的是将这些电台名称添加到tableview，并为每个电台名称的第一个字母添加一个部分。应跳过那些没有任何电台的部分。

第一部分应称为“ - ”，并应显示最近的电台。

示例：

--A--
Astation C
Alaska C
Alabama C
--C--
Cstation
Cathedral station
Central station

所以我得到了所有这些工作，但我觉得我做得很多，应该有一个更简单的方法。此外，在我的iPhone 4上加载此视图时，应用程序挂起1秒钟。这也不好。 这是我的代码：

- (void)viewDidLoad{
    self.filteredListContent = [NSMutableArray array];

    UIBarButtonItem *rightBarButton = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemSearch
                                                                                    target:self
                                                                                    action:@selector(searchBar:)];
    self.navigationItem.rightBarButtonItem = rightBarButton;

    [rightBarButton release];

    UISearchBar *mySearchBar = [[UISearchBar alloc] init];
    mySearchBar.delegate = self;
    [mySearchBar setAutocapitalizationType:UITextAutocapitalizationTypeNone];
    [mySearchBar sizeToFit];
    theTable.tableHeaderView = mySearchBar;

    if (UIInterfaceOrientationLandscapeRight == [[UIDevice currentDevice] orientation] ||
        UIInterfaceOrientationLandscapeLeft == [[UIDevice currentDevice] orientation])
    {
        theTable.tableHeaderView.frame = CGRectMake(0.f, 0.f, 480.f, 44.f);
    }
    else
    {
        theTable.tableHeaderView.frame = CGRectMake(0.f, 0.f, 320.f, 44.f);
    }

    searchDisplayController = [[UISearchDisplayController alloc] initWithSearchBar:mySearchBar contentsController:self];
    [self setSearchDisplayController:searchDisplayController];
    [searchDisplayController setDelegate:self];
    [searchDisplayController setSearchResultsDataSource:self];

    [mySearchBar release];

    /* Set the data */
    NSArray *stationenPath = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *stationenDocumentsDirectory = [stationenPath objectAtIndex:0];
    NSString *path = [stationenDocumentsDirectory stringByAppendingPathComponent:@"stations.plist"];

    NSDictionary* stationenDictionary = [[[NSDictionary alloc] initWithContentsOfFile:path] autorelease];
    xmlStationenList* stationsXml = [[xmlStationenList alloc] initWithDictionary:stationenDictionary];

    NSSortDescriptor *stationSorter = [[NSSortDescriptor alloc] initWithKey:@"_station" ascending:YES];
    NSMutableArray *xmlResult = [stationsXml getTimeResult];

    NSArray *objects = [[[NSArray alloc] initWithObjects:stationSorter,nil] autorelease];
    [xmlResult sortUsingDescriptors:objects];

    [stationSorter release];

    /* prefName is decided by the page opening chooseStationViewController. Using this class init function */
    NSUserDefaults *prefs = [NSUserDefaults standardUserDefaults];
    self.prefValue = [prefs valueForKey:prefName];

    self.listContent = [NSMutableArray array];

    for (stationenListSet *theList in xmlResult)
    {
        [self.listContent addObject:[theList get_station]];
    }
    /* END set the data */

    /* Set sections */
    self.sectionArray = [NSMutableArray array];
    [self.sectionArray addObject:@"-"];
    [self.sectionArray addObject:@"A"];
    [self.sectionArray addObject:@"B"];
    [self.sectionArray addObject:@"C"];
    [self.sectionArray addObject:@"D"];
    [self.sectionArray addObject:@"E"];
    [self.sectionArray addObject:@"F"];
    [self.sectionArray addObject:@"G"];
    [self.sectionArray addObject:@"H"];
    [self.sectionArray addObject:@"I"];
    [self.sectionArray addObject:@"J"];
    [self.sectionArray addObject:@"K"];
    [self.sectionArray addObject:@"L"];
    [self.sectionArray addObject:@"M"];
    [self.sectionArray addObject:@"N"];
    [self.sectionArray addObject:@"O"];
    [self.sectionArray addObject:@"P"];
    [self.sectionArray addObject:@"Q"];
    [self.sectionArray addObject:@"R"];
    [self.sectionArray addObject:@"S"];
    [self.sectionArray addObject:@"T"];
    [self.sectionArray addObject:@"U"];
    [self.sectionArray addObject:@"V"];
    [self.sectionArray addObject:@"W"];
    [self.sectionArray addObject:@"X"];
    [self.sectionArray addObject:@"Y"];
    [self.sectionArray addObject:@"Z"];
    [self.sectionArray addObject:@"Å"];
    [self.sectionArray addObject:@"Ä"];
    [self.sectionArray addObject:@"Ö"];

    [sectionSubArray release];
    sectionSubArray = [[NSMutableArray alloc] init];
    NSMutableArray *sectionTempArray = [[NSMutableArray alloc] init];

    [sectionTempArray addObject:@"-"];
    [sectionSubArray addObject:[[NSArray alloc] init]];

    for(NSString *sectionChar in self.sectionArray)
    {
        sectionChar = [sectionChar uppercaseString];
        int i = 0;

        NSMutableArray *sectionRowArray = [[NSMutableArray alloc] init];
        for (NSString* theStation in listContent)
        {
            NSString *firstChar = [[NSString alloc] initWithFormat:@"%C", toupper([theStation characterAtIndex:0])];

            if([firstChar isEqualToString:sectionChar])
            {
                [sectionRowArray addObject:theStation];

                i++;
            }

           [firstChar release];
        }

        if(i > 0)
        {
            [sectionSubArray addObject:sectionRowArray];
            [sectionTempArray addObject:sectionChar];
        }

       [sectionRowArray release];
    }

    self.sectionArray = sectionTempArray;
    [sectionTempArray release];

    [theTable reloadData];
    theTable.scrollEnabled = YES;
    [stationsXml release];

    locationManager = [[CLLocationManager alloc] init];
    locationManager.delegate=self;
    locationManager.desiredAccuracy=kCLLocationAccuracyBest;

    [locationManager startUpdatingLocation];
}

我做的愚蠢的事情是，我为每个字母循环通过我的300多个对象的数组。但我无法找到更好的方法来做到这一点。

最好的问候，
保罗佩伦

--------结果--------
由于您的所有答案，这就是结果：

- (void)viewDidLoad{
    self.filteredListContent = [NSMutableArray array];

    UIBarButtonItem *rightBarButton = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemSearch
                                                                                    target:self
                                                                                    action:@selector(searchBar:)];
    self.navigationItem.rightBarButtonItem = rightBarButton;

    [rightBarButton release];

    UISearchBar *mySearchBar = [[UISearchBar alloc] init];
    mySearchBar.delegate = self;
    [mySearchBar setAutocapitalizationType:UITextAutocapitalizationTypeNone];
    [mySearchBar sizeToFit];
    theTable.tableHeaderView = mySearchBar;

    if (UIInterfaceOrientationLandscapeRight == [[UIDevice currentDevice] orientation] ||
        UIInterfaceOrientationLandscapeLeft == [[UIDevice currentDevice] orientation])
    {
        theTable.tableHeaderView.frame = CGRectMake(0.f, 0.f, 480.f, 44.f);
    }
    else
    {
        theTable.tableHeaderView.frame = CGRectMake(0.f, 0.f, 320.f, 44.f);
    }

    searchDisplayController = [[UISearchDisplayController alloc] initWithSearchBar:mySearchBar contentsController:self];
    [self setSearchDisplayController:searchDisplayController];
    [searchDisplayController setDelegate:self];
    [searchDisplayController setSearchResultsDataSource:self];

    [mySearchBar release];

    /* Set the data */
    NSArray *stationenPath = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *stationenDocumentsDirectory = [stationenPath objectAtIndex:0];
    NSString *path = [stationenDocumentsDirectory stringByAppendingPathComponent:@"stations.plist"];

    NSDictionary* stationenDictionary = [[[NSDictionary alloc] initWithContentsOfFile:path] autorelease];
    xmlStationenList* stationsXml = [[xmlStationenList alloc] initWithDictionary:stationenDictionary];

    NSSortDescriptor *stationSorter = [[NSSortDescriptor alloc] initWithKey:@"_station" ascending:YES];
    NSMutableArray *xmlResult = [stationsXml getTimeResult];

    NSArray *objects = [[[NSArray alloc] initWithObjects:stationSorter,nil] autorelease];
    [xmlResult sortUsingDescriptors:objects];

    [stationSorter release];

    /* prefName is decided by the page opening chooseStationViewController. Using this class init function */
    NSUserDefaults *prefs = [NSUserDefaults standardUserDefaults];
    self.prefValue = [prefs valueForKey:prefName];

    self.listContent = [NSMutableArray array];

    for (stationenListSet *theList in xmlResult)
    {
        [self.listContent addObject:[theList get_station]];
    }
    /* END set the data */

    /* Set sections */
    self.sectionArray = [[NSArray alloc] initWithObjects:@"-", @"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", @"Å", @"Ä", @"Ö", nil];

    NSMutableDictionary *sectionDictionary = [NSMutableDictionary dictionaryWithObjectsAndKeys:
                                              [[NSMutableArray alloc] init], @"-", 
                                              [[NSMutableArray alloc] init], @"A", 
                                              [[NSMutableArray alloc] init], @"B",
                                              [[NSMutableArray alloc] init], @"C",
                                              [[NSMutableArray alloc] init], @"D",
                                              [[NSMutableArray alloc] init], @"E",
                                              [[NSMutableArray alloc] init], @"F", 
                                              [[NSMutableArray alloc] init], @"G", 
                                              [[NSMutableArray alloc] init], @"H", 
                                              [[NSMutableArray alloc] init], @"I", 
                                              [[NSMutableArray alloc] init], @"J", 
                                              [[NSMutableArray alloc] init], @"K", 
                                              [[NSMutableArray alloc] init], @"L", 
                                              [[NSMutableArray alloc] init], @"M", 
                                              [[NSMutableArray alloc] init], @"N", 
                                              [[NSMutableArray alloc] init], @"O", 
                                              [[NSMutableArray alloc] init], @"P", 
                                              [[NSMutableArray alloc] init], @"Q", 
                                              [[NSMutableArray alloc] init], @"R", 
                                              [[NSMutableArray alloc] init], @"S", 
                                              [[NSMutableArray alloc] init], @"T", 
                                              [[NSMutableArray alloc] init], @"U", 
                                              [[NSMutableArray alloc] init], @"V", 
                                              [[NSMutableArray alloc] init], @"W", 
                                              [[NSMutableArray alloc] init], @"X", 
                                              [[NSMutableArray alloc] init], @"Y", 
                                              [[NSMutableArray alloc] init], @"Z", 
                                              [[NSMutableArray alloc] init], @"Å", 
                                              [[NSMutableArray alloc] init], @"Ä", 
                                              [[NSMutableArray alloc] init], @"Ö", nil];

    [sectionSubArray release];
    sectionSubArray = [[NSMutableArray alloc] init];

    for(NSString *theStation in listContent) {
        NSString *firstChar = [[[NSString alloc] initWithFormat:@"%C", toupper([theStation characterAtIndex:0])] uppercaseString];

        [[sectionDictionary objectForKey:firstChar] addObject:theStation];
    }

    NSArray *keys = [sectionDictionary allKeys];
    keys = [keys sortedArrayUsingSelector:@selector(localizedCompare:)];

    int indexPath = 0;

    NSMutableArray *sectionTempArray = [[NSMutableArray alloc] init];

    [sectionTempArray addObject:@"-"];
    [sectionSubArray addObject:[[NSArray alloc] init]];

    for(NSString *key in keys)
    {
        if ([[sectionDictionary objectForKey:key] count] > 0)
        {
            NSArray *subArray = [[sectionDictionary objectForKey:key] sortedArrayUsingSelector:@selector(localizedCaseInsensitiveCompare:)];

            [sectionTempArray addObject:key];
            [sectionSubArray addObject:subArray];
        }

        indexPath++;
    }

    self.sectionArray = sectionTempArray;
    [sectionTempArray release];

    [theTable reloadData];
    theTable.scrollEnabled = YES;
    [stationsXml release];

    locationManager = [[CLLocationManager alloc] init];
    locationManager.delegate=self;
    locationManager.desiredAccuracy=kCLLocationAccuracyBest;

    [locationManager startUpdatingLocation];
}

Answer 1

这是带有fiew更改的代码。这些是我所做的改变：

1）使用局部变量而不是加载sectionArray 26次 2）循环站一次而不是29次

你有没有把代码留在某个地方？ sectionSubArray未在此函数中定义，但似乎是局部变量。它也从未被分配给一个财产。

- (void)viewDidLoad{
    self.filteredListContent = [NSMutableArray array];

    UIBarButtonItem *rightBarButton = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemSearch
                                                                                target:self
                                                                                action:@selector(searchBar:)];
    self.navigationItem.rightBarButtonItem = rightBarButton;

    [rightBarButton release];

    UISearchBar *mySearchBar = [[UISearchBar alloc] init];
    mySearchBar.delegate = self;
    [mySearchBar setAutocapitalizationType:UITextAutocapitalizationTypeNone];
    [mySearchBar sizeToFit];
    theTable.tableHeaderView = mySearchBar;

    if (UIInterfaceOrientationLandscapeRight == [[UIDevice currentDevice] orientation] ||
    UIInterfaceOrientationLandscapeLeft == [[UIDevice currentDevice] orientation])
    {
        theTable.tableHeaderView.frame = CGRectMake(0.f, 0.f, 480.f, 44.f);
    }
    else
    {
        theTable.tableHeaderView.frame = CGRectMake(0.f, 0.f, 320.f, 44.f);
    }

    searchDisplayController = [[UISearchDisplayController alloc] initWithSearchBar:mySearchBar contentsController:self];
    [self setSearchDisplayController:searchDisplayController];
    [searchDisplayController setDelegate:self];
    [searchDisplayController setSearchResultsDataSource:self];

    [mySearchBar release];

    /* Set the data */
    NSArray *stationenPath = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *stationenDocumentsDirectory = [stationenPath objectAtIndex:0];
    NSString *path = [stationenDocumentsDirectory stringByAppendingPathComponent:@"stations.plist"];

    NSDictionary* stationenDictionary = [[[NSDictionary alloc] initWithContentsOfFile:path] autorelease];
    xmlStationenList* stationsXml = [[xmlStationenList alloc] initWithDictionary:stationenDictionary];

    NSSortDescriptor *stationSorter = [[NSSortDescriptor alloc] initWithKey:@"_station" ascending:YES];
    NSMutableArray *xmlResult = [stationsXml getTimeResult];

    NSArray *objects = [[[NSArray alloc] initWithObjects:stationSorter,nil] autorelease];
    [xmlResult sortUsingDescriptors:objects];

    [stationSorter release];

    /* prefName is decided by the page opening chooseStationViewController. Using this class init function */
    NSUserDefaults *prefs = [NSUserDefaults standardUserDefaults];
    self.prefValue = [prefs valueForKey:prefName];

    self.listContent = [NSMutableArray array];

    for (stationenListSet *theList in xmlResult)
    {
        [self.listContent addObject:[theList get_station]];
    }
    /* END set the data */

    /* Set sections */
    NSMutableArray *sectionTempArray = [NSMutableArray array];
    self.sectionArray = sectionTempArray;
    [sectionTempArray addObject:@"-"];
    [sectionTempArray addObject:@"A"];
    [sectionTempArray addObject:@"B"];
    [sectionTempArray addObject:@"C"];
    [sectionTempArray addObject:@"D"];
    [sectionTempArray addObject:@"E"];
    [sectionTempArray addObject:@"F"];
    [sectionTempArray addObject:@"G"];
    [sectionTempArray addObject:@"H"];
    [sectionTempArray addObject:@"I"];
    [sectionTempArray addObject:@"J"];
    [sectionTempArray addObject:@"K"];
    [sectionTempArray addObject:@"L"];
    [sectionTempArray addObject:@"M"];
    [sectionTempArray addObject:@"N"];
    [sectionTempArray addObject:@"O"];
    [sectionTempArray addObject:@"P"];
    [sectionTempArray addObject:@"Q"];
    [sectionTempArray addObject:@"R"];
    [sectionTempArray addObject:@"S"];
    [sectionTempArray addObject:@"T"];
    [sectionTempArray addObject:@"U"];
    [sectionTempArray addObject:@"V"];
    [sectionTempArray addObject:@"W"];
    [sectionTempArray addObject:@"X"];
    [sectionTempArray addObject:@"Y"];
    [sectionTempArray addObject:@"Z"];
    [sectionTempArray addObject:@"Å"];
    [sectionTempArray addObject:@"Ä"];
    [sectionTempArray addObject:@"Ö"];

    [sectionSubArray release];
    sectionSubArray = [[NSMutableArray alloc] init];
    sectionTempArray = [[NSMutableArray alloc] init];

    [sectionTempArray addObject:@"-"];
    [sectionSubArray addObject:[[NSArray alloc] init]];

    NSMutableArray *sectionRowArrays[29];
    memset(sectionRowArrays,0,sizeof(NSMutableArray*)*29);
    for(NSString *theStation in listContent) {
        char currChar = toupper([theStation characterAtIndex:0]);
        uint8_t index;
        if(currChar == 'Å') index = 26;
          else if(currChar == 'Ä') index = 27;
          else if(currChar == 'Ö') index = 28;
          else index = currChar - 'A';
        if(!sectionRowArrays[index]) sectionRowArrays[index] = [[NSMutableArray alloc] init];
        [sectionRowArrays[index] addObject:theStation];
    }
    for(uint8_t index = 0; index < 29; ++index) {
        if(sectionRowArrays[index]) {
            [sectionSubArray addObject:sectionRowArrays[index]];
            NSString *currChar;
            if(index == 26) currChar = @"Å";
              else if(index == 27) currChar = @"Ä";
              else if(index == 28) currChar = @"Ö";
              else currChar = [NSString stringWithFormat:@"%c",index+'A'];
            [sectionTempArray addObject:currChar];
            [sectionRowArrays[index] release];
        }
    }

    self.sectionArray = sectionTempArray;
    [sectionTempArray release];

    [theTable reloadData];
    theTable.scrollEnabled = YES;
    [stationsXml release];

    locationManager = [[CLLocationManager alloc] init];
    locationManager.delegate=self;
    locationManager.desiredAccuracy=kCLLocationAccuracyBest;

    [locationManager startUpdatingLocation];
}

Answer 2

如何迭代站点列表并简单地将每个站点添加到相应的“桶”中？

如果您不需要NSObjects和NSArrays，那么您可以考虑使用标准模板库'map＆lt;＆gt;模板。但是如果你不熟悉它，那么它可能会带来更多的复杂性（就学习曲线而言）而不是它的价值。

简而言之，NSMtringDictionary如何使用NSString键作为第一个字母，而对象是NSMutableArrays。

我还没有这样做 - 但它会将你的30x300迭代减少到300。

Answer 3

如果您想花时间改进需要时间的代码，则需要对应用的执行情况进行分析。

提示1：在这里使用unichar，它将节省数百或数千个分配：

NSString *firstChar = [[NSString alloc] initWithFormat:@"%C", toupper([theStation characterAtIndex:0])];

提示2：使用增量增长填充了几个集合。它将有助于尽可能减少增长/重新分配的数量。苹果的第二个猜测已经存在，所以他们基于现实世界使用的优化有时会对你有利，但不一定总是如此。如果你在人口中过度分配了你的馆藏，你可以通过创建一个副本然后处理临时文件来展平它们。

提示3：尽可能避免自动释放的对象。 （严重）

当然，您也希望优化搜索/排序/填充算法。

但严重的是，如果您想了解您的时间花在哪里，您必须进行分析。

祝你好运！

Answer 4

只是添加其他答案，因为这是一个小得多的东西，并不是那么重要，但你应该至少知道一些。

此：

NSMutableArray *sectionTempArray = [NSMutableArray array];
self.sectionArray = sectionTempArray;
[sectionTempArray addObject:@"-"];
[sectionTempArray addObject:@"A"];
[sectionTempArray addObject:@"B"];
[sectionTempArray addObject:@"C"];
[sectionTempArray addObject:@"D"];
[sectionTempArray addObject:@"E"];
[sectionTempArray addObject:@"F"];
[sectionTempArray addObject:@"G"];
[sectionTempArray addObject:@"H"];
[sectionTempArray addObject:@"I"];
[sectionTempArray addObject:@"J"];
[sectionTempArray addObject:@"K"];
[sectionTempArray addObject:@"L"];
[sectionTempArray addObject:@"M"];
[sectionTempArray addObject:@"N"];
[sectionTempArray addObject:@"O"];
[sectionTempArray addObject:@"P"];
[sectionTempArray addObject:@"Q"];
[sectionTempArray addObject:@"R"];
[sectionTempArray addObject:@"S"];
[sectionTempArray addObject:@"T"];
[sectionTempArray addObject:@"U"];
[sectionTempArray addObject:@"V"];
[sectionTempArray addObject:@"W"];
[sectionTempArray addObject:@"X"];
[sectionTempArray addObject:@"Y"];
[sectionTempArray addObject:@"Z"];
[sectionTempArray addObject:@"Å"];
[sectionTempArray addObject:@"Ä"];
[sectionTempArray addObject:@"Ö"];

可以替换为：

NSArray sectionTempArray = [[NSArray alloc] initWithObjects: @"-", @"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", 
    @"Å", @"Ä", @"Ö", nil];

消除了对Mutable数组的需求（减少开销），如果编译器不能优化那些30个addObject调用，那么可以加快速度。如果在初始化之后不需要更改NSArray（或NSString或NSDictionary等）的内容，请不要使用Mutable版本，如果可以的话。