iOS PDF文件連接轉化為img圖片保存到相冊

{

    //self.passURL 是后台返回的可以加載顯示到webView中的PDF鏈接
    if ([self.passURL isEqualToString:@""] || self.passURL == nil || [self.passURL isEqual:nil] || !self.passURL) {
        [self InvalidAlertView];
        return;
    }
    NSURL *url = [[NSURL alloc] initWithString:self.passURL];
    CFURLRef ref = (__bridge CFURLRef)url;
    pdf = CGPDFDocumentCreateWithURL(ref);
    CFRelease(ref);
    
    CGImageRef imageRef = PDFPageToCGImage(1,pdf);
    UIImage *amg = [UIImage imageWithCGImage:imageRef];
    CGImageRelease(imageRef);
    
    //保存圖片到相冊
    UIImageWriteToSavedPhotosAlbum(amg, self, @selector(image:didFinishSavingWithError:contextInfo:), nil);
    
}

- (void)image:(UIImage *)image didFinishSavingWithError:(NSError *)error contextInfo:(void *)contextInfo{
    
    if (error == nil) {
        
        UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"提示" message:@"圖片已保存到相冊" delegate:self cancelButtonTitle:nil otherButtonTitles:@"好的", nil];
        [alert show];
    }else{
        
        UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"提示" message:@"保存失敗" delegate:self cancelButtonTitle:nil otherButtonTitles:@"確定", nil];
        [alert show];
    }
    
}

 

問題：在dealloc中 寫CGPDFDocumentRelease(pdf)這個方法，如果保存完照片后，快速點擊返回按鈕會崩潰，如果等2秒后點擊返回不會崩，所以在項目中先屏蔽掉了。

如果有哪位解決了不崩潰，請留個言，謝過了

- (void)dealloc {

   // CGPDFDocumentRelease(pdf);

    if ([self.mainWebView isLoading]){

        [self.mainWebView stopLoading];

    }

}