Laravel多重关系计数

Question

我有这些模特： ForumCategory 论坛 话题 回复

在主论坛页面中，我想计算并显示与此论坛相关的回复数量。 所有模型都有关系。

这是观点：

%binomial coefficients
function nk=nchoosek2(n, k)
    if n-k > k
        nk = prod((k+1:n) .* prod((1:n-k).^ (-1/(n-k))));
    else
        nk = prod((n-k+1:n) .* prod((1:k).^ (-1/k)) ) ;
    end
end
%function to store and retrieve results of nchoosek to/from a table
function ret = choose (n,k, D, K1, K2)
    persistent binTable = zeros(max([D+1,K1+K2+1]) , D+1);
    if binTable(n+1,k+1) == 0
        binTable(n+1,k+1) = nchoosek2(n,k);
    end
    ret = binTable(n+1,k+1);
end

function P = tst()
    P=0;k1=150; k2=150; D=200; P=0;
    choose(1,0,D,k1,k2);
    for i = 0:D-1
        for j = j=max(i - k2 , 0):min (i,k1-1)
            P=P+choose(k1,j)*choose(k2,i-j)/choose((k1+k2),i);
        end
    end
end

此行不起作用：

@foreach ($categories as $category)
<div class="panel-body">
    <div class="row">
        <div class="col-md-12">
            <div class="panel panel-default striped">
                <div class="panel-heading">
                    <div class="row">
                        <div class="col-md-11"><a href="#">{{ $category->name }}</a></div>
                        <div class="col-md-1 text-right"><a><span class="fa fa-arrow-down"></span></a></div>
                    </div>
                </div>
                @foreach ($category->forums as $forum)
                <div class="panel-body">
                    <div class="row">
                        <div class="col-md-1 text-right"><span class="fa fa-envelope fa-4x"></span></div>
                        <div class="col-md-7">
                            <h4>
                                <a href="forum/{{ $forum->id }}/{{ urlencode($forum->name) }}">{{ $forum->name }} </a>
                                <br>
                                <small>{{ $forum->description }}</small>
                            </h4>
                        </div>
                        <div class="col-md-1 post-num">
                            <h5>{{ $forum->topics->count() }}<br>
                            <small>Topics</small></h5>
                            <h5>{{ $forum->topics->replies->count() }}<br>
                            <small>Replies</small></h5>                         
                        </div>
                        <div class="col-md-3">
                            <img src="" class="img-circle last-comnt-img">
                            <a href="#">Last comment</a><br>
                            By <a href="#">Username</a><br>
                            <span class="text-muted">12:31</span>
                        </div>                      
                    </div>
                </div>
                @endforeach
            </div>
        </div>
    </div>
</div>
@endforeach