iOS WKWebView导致ViewController不调用

本文主要解决WKWebView在通过WKUserContentController添加MessageHandler方法用于JS调用Native导致ViewController内存泄露，无法正常释放。

1.ViewController没有调用dealloc可能的原因

之后检查了ViewController中所有使用到self的地方，发现WKUserContentController的下面这个方法有使用到self:
App注册方法用于JS调用

- (void)addScriptMessageHandler:(id <WKScriptMessageHandler>)scriptMessageHandler name:(NSString *)name

WKWebViewConfiguration *wkConfig = [[WKWebViewConfiguration alloc] init];
wkConfig.userContentController = [[WKUserContentController alloc] init];
[wkConfig.userContentController addScriptMessageHandler:self name:@"Native"];

2. 解决方案

(1)WeakScriptMessageDelegate

可以创建一个新的类WeakScriptMessageDelegate，也可以将@interface-@end写在ViewController.h中，@implementation-@end写在ViewController.m中。

@interface WeakScriptMessageDelegate : NSObject<WKScriptMessageHandler>

@property (nonatomic, weak) id<WKScriptMessageHandler> scriptDelegate;

- (instancetype)initWithDelegate:(id<WKScriptMessageHandler>)scriptDelegate;

@end

@implementation WeakScriptMessageDelegate

- (instancetype)initWithDelegate:(id<WKScriptMessageHandler>)scriptDelegate {
    self = [super init];
    if (self) {
        _scriptDelegate = scriptDelegate;
    }
    return self;
}

- (void)userContentController:(WKUserContentController *)userContentController didReceiveScriptMessage:(WKScriptMessage *)message {
    [self.scriptDelegate userContentController:userContentController didReceiveScriptMessage:message];
}

@end

(2)使用

添加了下面这行代码之后ViewController就会调用dealloc方法，此时ViewController已经正常释放。但是WeakScriptMessageDelegate没有释放，需要在dealloc中将WeakScriptMessageDelegate释放掉。

WKWebViewConfiguration *wkConfig = [[WKWebViewConfiguration alloc] init];
wkConfig.userContentController = [[WKUserContentController alloc] init];
[wkConfig.userContentController addScriptMessageHandler:[[WeakScriptMessageDelegate alloc] initWithDelegate:self] name:@"Native"];

(3)释放WeakScriptMessageDelegate

- (void)dealloc {
    [self.wkConfig.userContentController removeScriptMessageHandlerForName:@"Native"];
}