有什么方法可以访问NSArray元素valueForKeyPath吗？例如，谷歌的反向地理编码服务返回一个非常复杂的数据结构。如果我想得到这座城市，现在我必须把它分成两个电话，像这样：
NSDictionary *address = [NSString stringWithString:[[[dictionary objectForKey:@"Placemark"] objectAtIndex:0] objectForKey:@"address"]];
NSLog(@"%@", [address valueForKeyPath:@"AddressDetails.Country.AdministrativeArea.SubAdministrativeArea.Locality.LocalityName"]);
只是想知道是否有办法将objectAtIndex:调用硬塞到valueForKeyPath字符串中。我尝试了类似 @"Placemark[0].address" 的 javascript-esque 公式，但没有骰子。
很不幸的是，不行。关于允许使用键值编码的完整文档在这里。据我所知，没有任何运算符可以让您获取特定数组或设置对象。
这是我刚刚为 NSObject 编写的一个可以处理数组索引的类别，因此您可以访问这样的嵌套对象：“person.friends[0].name”
@interface NSObject (ValueForKeyPathWithIndexes)
-(id)valueForKeyPathWithIndexes:(NSString*)fullPath;
@end
#import "NSObject+ValueForKeyPathWithIndexes.h"
@implementation NSObject (ValueForKeyPathWithIndexes)
-(id)valueForKeyPathWithIndexes:(NSString*)fullPath
{
NSRange testrange = [fullPath rangeOfString:@"["];
if (testrange.location == NSNotFound)
return [self valueForKeyPath:fullPath];
NSArray* parts = [fullPath componentsSeparatedByString:@"."];
id currentObj = self;
for (NSString* part in parts)
{
NSRange range1 = [part rangeOfString:@"["];
if (range1.location == NSNotFound)
{
currentObj = [currentObj valueForKey:part];
}
else
{
NSString* arrayKey = [part substringToIndex:range1.location];
int index = [[[part substringToIndex:part.length-1] substringFromIndex:range1.location+1] intValue];
currentObj = [[currentObj valueForKey:arrayKey] objectAtIndex:index];
}
}
return currentObj;
}
@end
像这样使用它
NSString* personsFriendsName = [obj valueForKeyPathsWithIndexes:@"me.friends[0].name"];
没有错误检查，所以它很容易出错，但你明白了。
您可以在持有 NSArray 的对象中截取 keypath。
在您的情况下，键路径将变为 Placemark0.address... Override valueForUndefinedKey; 在 keypath 中查找索引；像这样的东西：
-(id)valueForUndefinedKey:(NSString *)key
{
// Handle paths like Placemark0, Placemark1, ...
if ([key hasPrefix:@"Placemark"])
{
// Caller wants to access the Placemark array.
// Find the array index they're after.
NSString *indexString = [key stringByReplacingOccurrencesOfString:@"Placemark" withString:@""];
NSInteger index = [indexString integerValue];
// Return array element.
if (index < self.placemarks.count)
return self.placemarks[index];
}
return [super valueForUndefinedKey:key];
}
这对于Mantle等模型框架非常有效。
用于NSArrayController此目的，因为NSObjectController不包括NSArrayController' 提供的对绑定数组元素更改的处理。如果您改用相同的代码NSObjectController，那么将 Cocoa Bindings 与您的NSObjectController实例一起使用只会在绑定时设置（绑定接口元素的）值，但不会接收来自数组元素的消息作为回报。通过NSObjectController用于此目的，即使contentObject已更新，用户界面也不会继续更新。只需使用相同的代码，NSArrayController还包括对数组的适当支持——这是手头的事情。
#import <Cocoa/Cocoa.h>
@interface DelvingArrayController : NSArrayController
@end
#import "DelvingArrayController.h"
@implementation DelvingArrayController
-(id)valueForKeyPath:(NSString *)keyPath
{
NSError *error = nil;
NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:@"^(.+?)\\[(\\d+?)\\]$" options:NSRegularExpressionCaseInsensitive error:&error];
NSArray<NSString*> *components = [keyPath componentsSeparatedByString:@"."];
id currentObject = self;
for (NSUInteger i = 0; i < components.count; i++)
{
if (![components[i] isEqualToString:@""])
{
NSTextCheckingResult *check_result = [regex firstMatchInString:components[i] options:0 range:NSMakeRange(0, components[i].length)];
if (!check_result)
currentObject = [currentObject valueForKey:components[i]];
else
{
NSRange array_name_capture_range = [check_result rangeAtIndex:1];
NSRange number_capture_range = [check_result rangeAtIndex:2];
if (number_capture_range.location == NSNotFound)
currentObject = [currentObject valueForKey:components[i]];
else if (array_name_capture_range.location != NSNotFound)
{
NSString *array_name = [components[i] substringWithRange:array_name_capture_range];
NSUInteger array_index = [[components[i] substringWithRange:number_capture_range] integerValue];
currentObject = [currentObject valueForKey:array_name];
if ([currentObject count] > array_index)
currentObject = [currentObject objectAtIndex:array_index];
}
}
}
}
return currentObject;
}
//at some point... also override setValueForKeyPath :-)
@end
此代码使用NSRegularExpression，适用于 macOS 10.7+。setValueForKeyPath如果您想编写功能，我将它作为练习留给您使用相同的方法来覆盖。
假设我们想要一个小游戏，有一个显示问题的窗口并使用四个按钮显示多项选择选项。我们在 plist 中有问题和多项选择，如NSStrings，还有一个NSNumber或可选的BOOL条目来指示正确答案。我们希望将选项按钮绑定到数组中的选项，每个问题也存储在数组中。
这是包含一些与游戏Halo相关的琐事问题的示例 plist 。请注意，选项位于嵌套数组中。
在此示例中，我将NSObjectController *stringsController其用作整个 plist 文件DelvingArrayController *triviaController的控制器，并用作与琐事相关的 plist 条目的控制器。您可以简单地使用一个DelvingArrayController，但我提供这个以供您理解。
琐事窗口非常简单，所以我只是使用 MainMenu.xib 中的 Interface Builder 来设计它：
的子类NSDocumentController用于通过NSMenuItem在 Interface Builder 中添加的显示琐事窗口。这个子类的实例也在.xib中，所以如果我们想使用.xib中的接口元素，我们必须等待Application Delegate实例的- (void)applicationDidFinishLaunching:(NSNotification *)aNotification方法，否则等到.xib加载完成...
#import <Cocoa/Cocoa.h>
#import "MenuInterfaceDocumentController.h"
@interface AppDelegate : NSObject <NSApplicationDelegate>
@property IBOutlet MenuInterfaceDocumentController *PrimaryInterfaceController;
@end
#import "AppDelegate.h"
@interface AppDelegate ()
@end
@implementation AppDelegate
@synthesize PrimaryInterfaceController;
- (void)applicationDidFinishLaunching:(NSNotification *)aNotification {
if ([NSApp mainMenu])
{
[PrimaryInterfaceController configureTriviaWindow];
}
}
#import <Cocoa/Cocoa.h>
@interface MenuInterfaceDocumentController : NSDocumentController
{
IBOutlet NSMenuItem *MenuItemTrivia; // shows the Trivia window
IBOutlet NSWindow *TriviaWindow;
IBOutlet NSTextView *TriviaQuestionField;
IBOutlet NSButton *TriviaOption1, *TriviaOption2, *TriviaOption3, *TriviaOption4;
}
@property NSObjectController *stringsController;
-(void)configureTriviaWindow;
@end
#import "MenuInterfaceDocumentController.h"
@interface MenuInterfaceDocumentController ()
@property NSDictionary *languageDictionary;
@property DelvingArrayController *triviaController;
@property NSNumber *triviaAnswer;
@end
@implementation MenuInterfaceDocumentController
@synthesize stringsController, languageDictionary, triviaController, triviaAnswer;
// all this happens before the MainMenu is available, and before the AppDelegate is sent applicationDidFinishLaunching
-(instancetype)init
{
self = [super init];
if (self)
{
if (!stringsController)
stringsController = [NSObjectController new];
stringsController.editable = NO;
// check for the plist file, eventually applying the following
languageDictionary = [NSDictionary dictionaryWithContentsOfFile:[[NSBundle mainBundle] pathForResource:@"en" ofType:@"plist"]];
if (languageDictionary)
[stringsController setContent:languageDictionary];
if (!triviaController)
{
triviaController = [DelvingArrayController new];
[triviaController bind:@"contentArray" toObject:stringsController withKeyPath:@"selection.trivia" options:nil];
}
triviaController.editable = NO;
if (!triviaAnswer)
{
triviaAnswer = @0;
[self bind:@"triviaAnswer" toObject:triviaController withKeyPath:@"selection.answer" options:nil];
}
}
return self;
}
// if we ever do something like change the plist file to a duplicate plist file that is in a different language, use this kind of approach to keep the same trivia entry active
-(IBAction)changeLanguage:(id)sender
{
NSUInteger triviaQIndex = triviaController.selectionIndex;
if (sender == MenuItemEnglishLanguage)
{
if ([self changeLanguageTo:@"en" Notify:YES])
{
[self updateSelectedLanguageMenuItemWithLanguageString:@"en"];
if ([triviaController.content count] > triviaQIndex) // in case the plist files don't match
[triviaController setSelectionIndex:triviaQIndex];
}
else
[self displayAlertFor:CUSTOM_ALERT_TYPE_LANGUAGE_CHANGE_FAILED];
}
else if (sender == MenuItemGermanLanguage)
{
if ([self changeLanguageTo:@"de" Notify:YES])
{
[self updateSelectedLanguageMenuItemWithLanguageString:@"de"];
if ([triviaController.content count] > triviaQIndex)
[triviaController setSelectionIndex:triviaQIndex];
}
else
[self displayAlertFor:CUSTOM_ALERT_TYPE_LANGUAGE_CHANGE_FAILED];
}
}
-(void)configureTriviaWindow
{
[TriviaQuestionField bind:@"string" toObject:triviaController withKeyPath:@"selection.question" options:nil];
[TriviaOption1 bind:@"title" toObject:triviaController withKeyPath:@"selection.options[0]" options:nil];
[TriviaOption2 bind:@"title" toObject:triviaController withKeyPath:@"selection.options[1]" options:nil];
[TriviaOption3 bind:@"title" toObject:triviaController withKeyPath:@"selection.options[2]" options:nil];
[TriviaOption4 bind:@"title" toObject:triviaController withKeyPath:@"selection.options[3]" options:nil];
}
// this method is how you would manually set the value if you did not use binding:
-(void)updateTriviaAnswer
{
triviaAnswer = [triviaController valueForKeyPath:@"selection.answer"];
}
-(IBAction)changeTriviaQuestion:(id)sender
{
if (triviaController.selectionIndex >= [(NSArray*)triviaController.content count] - 1)
[triviaController setSelectionIndex:0];
else
[triviaController setSelectionIndex:(triviaController.selectionIndex + 1)];
}
-(IBAction)showTriviaWindow:(id)sender
{
[TriviaWindow makeKeyAndOrderFront:sender];
}
- (IBAction)TriviaOptionChosen:(id)sender
{
// tag integers 0 through 3 are assigned to the option buttons in Interface Builder
if ([sender tag] == triviaAnswer.integerValue)
[self changeTriviaQuestion:sender];
else
NSBeep();
}
@end
序列总结
NSObjectController *stringsController = [[NSObjectController alloc] initWithContent:[NSDictionary dictionaryWithContentsOfFile:[[NSBundle mainBundle] pathForResource:@"en" ofType:@"plist"]]];
DelvingArrayController *triviaController = [DelvingArrayController new];
[triviaController bind:@"contentArray" toObject:stringsController withKeyPath:@"selection.trivia" options:nil];
NSNumber *triviaAnswer = @0;
[self bind:@"triviaAnswer" toObject:triviaController withKeyPath:@"selection.answer" options:nil];
// bind to .xib's interface elements after the nib has finished loading, else the IBOutlets are null
[TriviaQuestionField bind:@"string" toObject:triviaController withKeyPath:@"selection.question" options:nil];
[TriviaOption1 bind:@"title" toObject:triviaController withKeyPath:@"selection.options[0]" options:nil];
[TriviaOption2 bind:@"title" toObject:triviaController withKeyPath:@"selection.options[1]" options:nil];
[TriviaOption3 bind:@"title" toObject:triviaController withKeyPath:@"selection.options[2]" options:nil];
[TriviaOption4 bind:@"title" toObject:triviaController withKeyPath:@"selection.options[3]" options:nil];
// when the user chooses the correct option, go to the next question
if ([sender tag] == triviaAnswer.integerValue)
{
if (triviaController.selectionIndex >= [(NSArray*)triviaController.content count] - 1)
[triviaController setSelectionIndex:0];
else
[triviaController setSelectionIndex:(triviaController.selectionIndex + 1)];
}
为 NSObject 创建支持数组的方法：
@interface NSObject(ArraySupported)
-(id)valueForKeySupportedArray:(NSString*)path;
-(id)valueForKeyPathSupportedArray:(NSString*)fullPath;
@end
@implementation NSObject(ArraySupported)
-(id)valueForKeySupportedArray:(NSString*)path {
id value = nil;
if ([self isKindOfClass:[NSArray class]]) {
NSArray *array = (NSArray *)self;
NSUInteger index = path.integerValue;
if (index >= 0 && index < array.count) {
value = array[index];
}
} else {
value = [self valueForKey:path];
}
return value;
}
-(id)valueForKeyPathSupportedArray:(NSString*)fullPath {
NSArray* parts = [fullPath componentsSeparatedByString:@"."];
id value = self;
for (NSString* part in parts) {
value = [value valueForKeySupportedArray:part];
if (value == nil) {
break;
}
}
return value;
}
@end
如何使用：
NSObject *object = @{@"Placemark":@[@{@"address":@"..."}]};
NSString *address = [object valueForKeyPathSupportedArray:@"Placemark.0.address"];
// address = "..."