iOS-JS和OC的交互

1.OC调⽤用JS - OC传递数据给JS
1> 利⽤用UIWebView的某个⽅方法执⾏行JS代码
NSString *result = [webView stringByEvaluatingJavaScriptFromString:js];
// result是执⾏行完JS代码后的返回值
// 其实也可以通过这个⽅方法办到:JS传递数据给OC
2> 举例
NSString *username = @"zhangsan";
NSString *pwd = @"888888";
NSMutableString *js = [NSMutableString string];
[js appendString:@"function login(username, pwd) { alert(username + '-' +
pwd);}"];
[js appendFormat:@"login('%@', '%@');", username, pwd];
// 在OC中调⽤用JS的函数(执⾏行JS代码)
[webView stringByEvaluatingJavaScriptFromString:js];

2.JS调⽤用OC - JS传递数据给OC

        /* 
         通用url的设计
         协议固定： xxx:
        一般有2个参数：
         1> 方法名
         2> 方法参数
         */
        NSString *onload = @"this.onclick = function() {"
                            "   window.location.href = 'xxx:saveImageToAlbum:&' + this.src;"
                            "};";
        [imgHtml appendFormat:@"<img onload="%@" width="%d" height="%d" src="%@">", onload, width, height, img.src];


#pragma mark - <UIWebViewDelegate>
/**
 *  每当webView发送一个请求之前都会先调用这个方法
 *
 *  @param request        即将发送的请求
 *
 *  @return YES: 允许发送这个请求, NO: 禁止发送这个请求
 */
- (BOOL)webView:(UIWebView *)webView shouldStartLoadWithRequest:(NSURLRequest *)request navigationType:(UIWebViewNavigationType)navigationType
{
    NSString *url = request.URL.absoluteString;
    // xxx:call:&10086
    // xxx:sendMsg:body:&10086&2434
    NSRange range = [url rangeOfString:@"xxx:"];
    if (range.location != NSNotFound) {
        NSUInteger loc = range.location + range.length;
        NSString *path = [url substringFromIndex:loc];
        // 获得方法和参数
        NSArray *methodNameAndParam = [path componentsSeparatedByString:@"&"];
        // 方法名
        NSString *methodName = [methodNameAndParam firstObject];
        // 调用方法
        SEL selector = NSSelectorFromString(methodName);
        if ([self respondsToSelector:selector]) { // 判断方法的目的： 防止因为方法不存在而报错
            NSMutableArray *params = nil;
            if (methodNameAndParam.count > 1) { // 方法有参数
                params = [NSMutableArray arrayWithArray:methodNameAndParam];
                // 从数组中去掉方法名
                [params removeObjectAtIndex:0];
            }
            [self performSelector:selector withObjects:params];
        }
        return NO;
    }
    return YES;
}
这里用到 performSelector: withObjects 方法 传递多个参数：

- (id)performSelector:(SEL)selector withObjects:(NSArray *)objects {
    NSMethodSignature *signature = [self methodSignatureForSelector:selector];
    if (signature) {
        NSInvocation* invocation = [NSInvocation invocationWithMethodSignature:signature];
        [invocation setTarget:self];
        [invocation setSelector:selector];
        for(int i = 0; i < [objects count]; i++){
            id object = [objects objectAtIndex:i];
            [invocation setArgument:&object atIndex: (i + 2)];
        }
        [invocation invoke];
        if (signature.methodReturnLength) {
            id anObject;
            [invocation getReturnValue:&anObject];
            return anObject;
        } else {
            return nil;
        }
    } else {
        return nil;
    }
}