ios – 具有预先实现的委托方法的子类对象

概述我正在尝试创建一个NSURLConnection的子类,它已经预先实现了一个委托方法. 我目前的方法是使用一个“代理”委托,它具有预填充此方法并调用其他方法,如下所示： -(BOOL)connectionShouldUseCredentialStorage:(NSURLConnection *)connection{if ([self.delegate respondsToSelector:@s 我正在尝试创建一个NSURLConnection的子类,它已经预先实现了一个委托方法.

我目前的方法是使用一个“代理”委托,它具有预填充此方法并调用其他方法,如下所示：

-(BOol)connectionShouldUseCredentialStorage:(NSURLConnection *)connection{if ([self.delegate respondsToSelector:@selector(connectionShouldUseCredentialStorage:)]) {    return [self.delegate connectionShouldUseCredentialStorage:connection];}else{    return NulL;}

}

delegate是实际用户定义的委托.这会导致某种问题,因为在某些情况下返回NulL会导致 *** 作停止.

这样做的正确方法是什么？

我的类最终应该有一个预先配置的方法调用,其他东西应该由dev实现.

编辑：另一个补充什么是voID委托方法的正确方法？

Edit2：另一个要求是子类应该像它的父类一样工作,但它必须预先实现一个委托方法.因此开发人员还可以实现NSURLConnection的另一个委托.无法看到如何使用自定义协议

解决方法 你可以做的是编写一个实现respondsToSelector：的nsproxy子类.像这样的东西：

URLConnectionProxyDelegate.h：

#import <Foundation/Foundation.h>@interface URLConnectionProxyDelegate : nsproxy <NSURLConnectionDelegate>- (instancetype)initWithDelegate:(ID<NSURLConnectionDelegate>)delegate;@end

URLConnectionProxyDelegate.m：

#import "URLConnectionProxyDelegate.h"@implementation URLConnectionProxyDelegate{    __weak ID<NSURLConnectionDelegate> _realDelegate;}#pragma mark - Object lifecycle- (instancetype)initWithDelegate:(ID<NSURLConnectionDelegate>)delegate{    if (self) {        _realDelegate = delegate;    }    return self;}#pragma mark - nsproxy OverrIDes- (NSMethodSignature *)methodSignatureForSelector:(SEL)sel{    return [(ID)_realDelegate methodSignatureForSelector:sel];}- (voID)forwardInvocation:(NSInvocation *)invocation{    invocation.target = _realDelegate;    [invocation invoke];}#pragma mark - NSObject Protocol Methods- (BOol)respondsToSelector:(SEL)sel{    // replace @selector(connection:dIDFailWithError:) with your actual pre-implemented method's selector    if (sel == @selector(connection:dIDFailWithError:)) {        return YES;    }    return [_realDelegate respondsToSelector:sel];}#pragma mark - NSURLConnectionDelegate Methods// Since I don't kNow which method your pre-implemented method is,// I just chose connection:dIDFailWithError: as an example. Replace this// with your actual pre-implemented method.- (voID)connection:(NSURLConnection *)connection dIDFailWithError:(NSError *)error{    NSLog(@"Connection Failed: This gets called only when the proxy delegate is used");}@end

然后在你的视图控制器类中使用这个类,你可以这样做：

SomeVIEwController.m：

#import "SomeVIEwController.h"#import "URLConnectionProxyDelegate.h"@interface SomeVIEwController () <NSURLConnectionDelegate>@end@implementation SomeVIEwController#pragma mark - button actions- (IBAction)testSuccessURLWithnormalDelegate:(ID)sender{    NSURL *url = [NSURL URLWithString:@"http://example.com"];    NSURLRequest *request = [NSURLRequest requestWithURL:url];    // Using self as the delegate    [NSURLConnection connectionWithRequest:request delegate:self];}- (IBAction)testFailURLWithnormalDelegate:(ID)sender{    NSURL *url = [NSURL URLWithString:@"not a real url"];    NSURLRequest *request = [NSURLRequest requestWithURL:url];    // Using self as the delegate    [NSURLConnection connectionWithRequest:request delegate:self];}- (IBAction)testSuccessURLWithProxyDelegate:(ID)sender{    NSURL *url = [NSURL URLWithString:@"http://example.com"];    NSURLRequest *request = [NSURLRequest requestWithURL:url];    // Using a proxy delegate,with self as the real delegate    URLConnectionProxyDelegate *proxy = [[URLConnectionProxyDelegate alloc] initWithDelegate:self];    [NSURLConnection connectionWithRequest:request delegate:proxy];}- (IBAction)testFailURLWithProxyDelegate:(ID)sender{    NSURL *url = [NSURL URLWithString:@"not a real url"];    NSURLRequest *request = [NSURLRequest requestWithURL:url];    // Using a proxy delegate,with self as the real delegate    URLConnectionProxyDelegate *proxy = [[URLConnectionProxyDelegate alloc] initWithDelegate:self];    [NSURLConnection connectionWithRequest:request delegate:proxy];}#pragma mark - NSURLConnectionDelegate Methods- (voID)connection:(NSURLConnection *)connection dIDFailWithError:(NSError *)error{    NSLog(@"Connection Failed: This gets called only when the vIEw controller is used as the delegate");}- (BOol)connectionShouldUseCredentialStorage:(NSURLConnection *)connection{    NSLog(@"Connection success: This gets called when the vIEw controller OR the proxy delegate is used as the delegate");    return YES;}@end

关于这一切的重要注意事项是URLConnectionProxyDelegate重写respondsToSelector：并将其传递给它的_realDelegate对象而不是调用super,如果选择器是你的“预实现”方法的选择器,它也总是返回YES.这意味着您甚至不必在NSURLConnectionDelegate协议中实现任何其他方法 – 您只需要实现“预先实现”的方法.

你甚至可以有几个预先实现的方法.只需在代理类的respondsToSelector中为选择器添加更多检查即可轻松完成：

[...]if (sel == @selector(connection:dIDFailWithError:)) {    return YES;}if (sel == @selector(connectionShouldUseCredentialStorage:)) {    return YES;}[...]

…然后只是确保在代理类中实现所有这些方法,当然：

[...]- (voID)connection:(NSURLConnection *)connection dIDFailWithError:(NSError *)error{    NSLog(@"pre-implemented connection:dIDFailWithError:");}- (BOol)connectionShouldUseCredentialStorage:(NSURLConnection *)connection{    NSLog(@"pre-implemented connectionShouldUseCredentialStorage:");    return YES;}[...]

希望这是有道理的,对你有所帮助.

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