项目需要对`WKWebView`进行Cookie同步，在网上找了好多方法，经过测试：
第一种（无效）：通过`evaluateJavaScript`注入，这种方法是注入不了Cookie的，因为js没有权限
第二种（无效）：通过请求头的方法，`[request setValue:@"cookie string" forHTTPHeaderField:@"Cookie"]`，这种方法js不能通过document.cookie获取到cookie
第二种：通过`addUserScript`方法，如果你的WKWebView已经登录了，只需要在`WKWebView`的初始化的时候注入一次就好了，但是如果你的`WKWebView`是要在页面上动态同步`Cookie`的话，还需要其它操作，下面是我的解决方案。

初始化WKWebView注入Cookie

- (instancetype)initWithFrame:(CGRect)frame configuration:(nonnull WKWebViewConfiguration *)configuration
{
    //一定要在[super initWithFrame:frame configuration:configuration]之前设置，否则无效
    WKUserContentController *userContentController = WKUserContentController.new;
    WKUserScript *cookieScript = [[WKUserScript alloc] initWithSource:[self updateCookies] injectionTime:WKUserScriptInjectionTimeAtDocumentStart forMainFrameOnly:NO];
    
    [userContentController addUserScript:cookieScript];
    configuration.userContentController = userContentController;
    
    self = [super initWithFrame:frame configuration:configuration];
    if (self) {
        self.scrollView.bounces = NO;
        self.scrollView.showsHorizontalScrollIndicator = NO;
        [self sizeToFit];
        self.backgroundColor = HSQColorGray250;
        self.allowsBackForwardNavigationGestures = YES;
        [self addSubview:self.progressView];
        [self addObserver:self forKeyPath:@"estimatedProgress" options:NSKeyValueObservingOptionNew | NSKeyValueObservingOptionInitial context:nil];
    }
    return self;
}

这里拼接是Cookie

- (NSString *)updateCookies
{
    NSMutableString *cookieValue = [NSMutableString stringWithFormat:@""];
    NSHTTPCookieStorage *cookieJar = [NSHTTPCookieStorage sharedHTTPCookieStorage];
    //这边是在登录接口保存了登录Cookie
    NSString *loginCookie = [[NSUserDefaults standardUserDefaults] objectForKey:kDMUserLoginCookie];
    
    NSMutableString *mHsqCookie = [[NSMutableString alloc] init];
    NSMutableString *mDwdCookie = [[NSMutableString alloc] init];
    
    for (NSHTTPCookie *cookie in cookieJar.cookies) {
    //这边是做域名拦截
        if ([cookie.domain containsString:@".xxxx.net"]) {
            NSString *hsqCookie = [NSString stringWithFormat:@"document.cookie='%@=%@;%@=%@';", cookie.name, cookie.value, @"domain", cookie.domain];
            //用来处理垮域问题
            NSString *dwdCookie = [NSString stringWithFormat:@"document.cookie='%@=%@;%@=%@';", cookie.name, cookie.value, @"domain", @"yyyy.net"];
            [mHsqCookie appendString:hsqCookie];
            [mDwdCookie appendString:dwdCookie];
        }
    }
    
    //拼接登录Cookie
    if (!IsNilOrNull(loginCookie) && ![cookieValue containsString:HsqSidCookie]) {
        [mHsqCookie appendString:[NSString stringWithFormat:@"document.cookie='%@domain=.xxxx.net';", loginCookie]];
        [mDwdCookie appendString:[NSString stringWithFormat:@"document.cookie='%@domain=yyyy.net';", loginCookie]];
    }
    
    [cookieValue appendString:mHsqCookie];
    [cookieValue appendString:mDwdCookie];

    return cookieValue;
}

接口请求拿到登录Cookie保存在本地

// 保存登录cookie
- (void)saveLoginCookie:(NSURLSessionDataTask *)task
{
    if ([task.response isKindOfClass:[NSHTTPURLResponse class]]) {
        NSHTTPURLResponse *response = (NSHTTPURLResponse *)task.response;
        NSDictionary *allFields = response.allHeaderFields;
        NSArray<NSHTTPCookie*> *cookies = [NSHTTPCookie cookiesWithResponseHeaderFields:allFields forURL:[NSURL URLWithString:[NSString stringWithFormat:@"api地址"]]];
        [cookies enumerateObjectsUsingBlock:^(NSHTTPCookie * _Nonnull obj, NSUInteger idx, BOOL * _Nonnull stop) {
            if ([obj.domain containsString:@".xxxx.net"] && [obj.name isEqualToString:HsqSidCookie] && ![obj.value isEqualToString:@"deleted"]) {
                NSString *hsqCookie = [NSString stringWithFormat:@"%@=%@;", obj.name, obj.value];
                [[NSUserDefaults standardUserDefaults] setObject:hsqCookie forKey:kDMUserLoginCookie];
                [[NSUserDefaults standardUserDefaults] synchronize];
                *stop = YES;
            }
        }];
    }
}

动态同步cookie

- (WKNavigation *)reload
{
    [self.configuration.userContentController removeAllUserScripts];
    
    WKUserScript * cookieScript = [[WKUserScript alloc] initWithSource:[self updateCookies] injectionTime:WKUserScriptInjectionTimeAtDocumentStart forMainFrameOnly:NO];
    [self.configuration.userContentController addUserScript:cookieScript];
    
    return [super reload];
}