iOS如何向UIWebView loadRequest添加完成块：？

Question

I'm working with a UIWebView and am already using webViewDidFinishLoad: method with an optional block that gets executed after loading complete:

    -(void)webViewDidFinishLoad:(UIWebView *)webView
    {
        [super webViewDidFinishLoad:webView];

//... bunch of other code        

        if(self.webViewFinishLoadBlock != nil)
        {
            self.webViewFinishLoadBlock();
        }
    }

Now I'm working with an even more complicated sequence of loading pages and redirects that makes the logic above not sufficient. I don't want to register myself as a delegate of dummyWebView and have to juggle multiple completion blocks stored in my view controller's properties:

    dummyWebView = [[UIWebView alloc] initWithFrame:CGRectZero];
    [dummyWebView loadRequest:[NSURLRequest requestWithURL:logoutURL]];
//Ideally here I would know when dummyWebView finishes loading, because there's some code I want to execute once it is done

My question is:

Is there some kind of third party framework that would allow me to use loadRequest:withCompletion: to simplify writing callback code?

Answer 1

You can just:

• Subclass UIWebView with a property to hold the webViewDidFinish completion block;

• Make sure it specifies its delegate;

• Implement the webViewDidFinish much like you wrote it (though I'd suggest the block return both the web view as well as the NSError object, if any); and

• Implement the webView:didFailLoadWithError: , too.

Thus:

//  MyWebView.h

#import <UIKit/UIKit.h>

typedef void(^WebViewFinishLoadBlock)(UIWebView *, NSError *);

@interface MyWebView : UIWebView

@property(nonatomic, copy) WebViewFinishLoadBlock webViewFinishLoadBlock;

- (void)loadRequest:(NSURLRequest *)request withCompletionHandler:(WebViewFinishLoadBlock)completionHandler;

@end

And

//  MyWebView.m

#import "MyWebView.h"

@interface MyWebView () <UIWebViewDelegate>
@end

@implementation MyWebView

- (void)loadRequest:(NSURLRequest *)request withCompletionHandler:(WebViewFinishLoadBlock)completionHandler
{
    self.delegate = self;
    self.webViewFinishLoadBlock = completionHandler;

    [self loadRequest:request];
}

#pragma mark - UIWebViewDelegate

- (void)webViewDidFinishLoad:(UIWebView *)webView
{
    if (self.webViewFinishLoadBlock) {
        self.webViewFinishLoadBlock(webView, nil);
        self.webViewFinishLoadBlock = nil;
    }
}

- (void)webView:(UIWebView *)webView didFailLoadWithError:(NSError *)error
{
    if (self.webViewFinishLoadBlock) {
        self.webViewFinishLoadBlock(webView, error);
        self.webViewFinishLoadBlock = nil;
    }
}

@end

And then:

MyWebView *webView = [[MyWebView alloc] init];
webView.frame = self.view.bounds;
[self.view addSubview:webView];

NSURLRequest *request = [NSURLRequest requestWithURL:url];
[webView loadRequest:request withCompletionHandler:^(UIWebView *webView, NSError *error) {
    if (error) {
        NSLog(@"failed: %@", error);
    } else {
        NSLog(@"succeeded");
    }
}];

Answer 2

- (void)webViewDidFinishLoad:(UIWebView *)webView

is a delegate method. By convention delegate methods require the object pass itself back to the delegate:

(UIWebView*)webView

Through a parameter.

If we want to get last request parameter using property request: that means webView.request.URL

The parent object can be the delegate for multiple objects, and it can identify which it is getting a response from though that parameter. Either switch on what responds to you or build some infrastructure to handle it more elegantly.