Question

我有以下代码：

NSDataDetector* detector = [NSDataDetector dataDetectorWithTypes:NSTextCheckingTypeLink error:nil];
NSArray* matches = [detector matchesInString:[[imagesArray valueForKey:@"content"] objectAtIndex:indexPath.row] options:0 range:NSMakeRange(0, [[[imagesArray valueForKey:@"content"] objectAtIndex:indexPath.row] length])];

这个结果在日志中：

<NSLinkCheckingResult: 0xa632220>{235, 75}{http://URL/wordpress/wp-content/uploads/2014/04/Digital-Board-2.png}
<NSLinkCheckingResult: 0xa64eb90>{280, 25}{http://www.w3schools.com/}

我需要的是检查它们包含图像的链接。在这种情况下，第一个链接包含图像（PNG）。第二个没有。我怎么能这样做？

Answer 1

您可以为他们获取NSURL，并将扩展名与图片扩展名列表进行比较。也许是这样的事情：

// A list of extensions to check against 
NSArray *imageExtensions = @[@"png", @"jpg", @"gif"]; //...

// Iterate & match the URL objects from your checking results
for (NSTextCheckingResult *result in matches) {
    NSURL *url = [result URL];
    NSString *extension = [url pathExtension];
    if ([imageExtensions containsObject:extension]) {
        NSLog(@"Image URL: %@", url);
        // Do something with it
    }
}

Answer 2

根据此answer，您可以使用HTTP HEAD请求并检查内容类型图像的可能内容类型列表为here。

代码示例：

- (void)executeHeadRequest:(NSURL *)url {
    NSMutableURLRequest *request = [[NSMutableURLRequest alloc] init];
    [request setURL:url];
    [request setHTTPMethod:@"HEAD"];
    [NSURLConnection connectionWithRequest:request delegate:self]
}

// Delegate methods
- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response {
    NSHTTPURLResponse *response = (NSHTTPURLResponse *)response;
    NSString *contentType = [response.allHeaderFields valueForKey:@"Content-Type"];
    // Check content type here
}

Answer 3

在Swift 3中，扩展名为：

extension String {

    public func isImage() -> Bool {
        // Add here your image formats.
        let imageFormats = ["jpg", "jpeg", "png", "gif"]

        if let ext = self.getExtension() {
            return imageFormats.contains(ext)           
        }

        return false
    }

    public func getExtension() -> String? {
       let ext = (self as NSString).pathExtension

       if ext.isEmpty {
           return nil
       }

       return ext
    }

    public func isURL() -> Bool {
       return URL(string: self) != nil
    }

}

然后在viewController（或您想要的任何地方）：

 let str = "string"

 // Check if the given string is an URL and an image 
 if str.isURL() && str.isImage() {
     print("image and url")
 }

注意：此方法适用于指向具有名称和扩展名的图像资源的网址，例如：http://www.yourwebapi.com/api/image.jpg，但它对于这样的网址不起作用：http://www.yourwebapi.com/api/images/12626因为在这种情况下，URL字符串并不能告诉我们关于mime类型的任何信息。

根据@Visput的建议，您应该查看Content-Type HTTP Header并检查返回的mime-type。例如，image/jpeg

Answer 4

当然，问题在于检查链接而不查看它们背后的资源是因为动态Web服务无法返回图像，但在网址上没有典型的图像扩展名。

您可能采取的另一种方法是尝试仅加载HTTP标头并检查返回的MIME类型。你可以做这个作为后台任务;只需加载标题字段，即可最大限度地减少流量。

这是您可能想要异步执行的同步版本。只是为了证明这个想法：

#import <Foundation/Foundation.h>

BOOL urlIsImage(NSURL *url)
{
    NSMutableURLRequest *request = [[NSURLRequest requestWithURL:url] mutableCopy];
    NSURLResponse *response = nil;
    NSError *error = nil;
    [request setValue:@"HEAD" forKey:@"HTTPMethod"];
    [NSURLConnection sendSynchronousRequest:request
                          returningResponse:&response
                                      error:&error];
    NSString *mimeType = [response MIMEType];
    NSRange range = [mimeType rangeOfString:@"image"];
    return (range.location != NSNotFound);
}

int main(int argc, const char * argv[])
{
    @autoreleasepool {
        NSArray *urlStrings = @[@"http://lorempixel.com/400/200/",
                                @"http://stackoverflow.com"];
        for( NSString *urlString in urlStrings ) {
            NSURL *url = [NSURL URLWithString:urlString];
            if( urlIsImage(url) ) {
                NSLog(@"%@ loads an image",urlString);
            }
            else {
                NSLog(@"%@ does *not* load an image",urlString);
            }
        }
    }
    return 0;
}

Answer 5

与Visputs答案类似，您可以从response.MIMEType获取MimeType。

这里是代码：

- (void)executeHeadRequest:(NSURL *)url {
  NSMutableURLRequest *request = [[NSMutableURLRequest alloc] init];
  [request setURL:url];
  [request setHTTPMethod:@"HEAD"];
  [NSURLConnection connectionWithRequest:request delegate:self]
}

// Delegate methods
- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response {
  NSLog(@"MIME: %@", response.MIMEType);
  // Check content type here
}

Answer 6

由于NSURLConnection已被弃用。

获取contentType的类似代码

- (void)executeHeadRequest:(NSURL *)url {

NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url];
[request setHTTPMethod:@"HEAD"];
NSURLSessionConfiguration *sessionConfig = [NSURLSessionConfiguration defaultSessionConfiguration];
NSURLSession *session = [NSURLSession sessionWithConfiguration:sessionConfig];

[[session dataTaskWithRequest:request completionHandler:^(NSData * _Nullable data, NSURLResponse * _Nullable response, NSError * _Nullable error) {
    if (!error) {

        NSHTTPURLResponse *httpResponse = (NSHTTPURLResponse *)response;
        NSString *contentType = [httpResponse.allHeaderFields valueForKey:@"Content-Type"];
        if ([contentType contains:@"image"]) {

            NSLog(@"Url is image type");
        }
    }
    [session invalidateAndCancel];
}] resume];

}

检查网址是否为图片

6 个答案: