Question

我在User和Role模型之间存在多对多的关系，并希望检查用户是否具有给定列表的任何角色。

所以我输入了模型：

public function hasAnyRoles(array $roles) {
    return $this->roles()->whereIn('name', $roles)->exists();
}

并UserController：

// User has only "manager" role.
$user->hasAnyRoles(['admin', 'manager']) // true

问题是在某些部分我需要验证用户是否具有给定列表的所有角色。例如：

// User has only "manager" role.
$user->hasRoles(['admin', 'manager']) // false

我在＆＃34; lazy＆＃34;模式，生成n + 1个查询：

public function hasRolesLazy($roles) {
    return array_reduce($roles, function ($initial, $role) {
        return $this->roles()->where('name', $role)->exists();
    }, false);
}

如何构造hasRoles(array $roles)方法只在数据库中执行一个查询？我是SQL的新手，所以我无法找到很多解决方案。

Answer 1

试试这个：

public function hasAnyRoles(array $roles) {
    return $this->whereHas('roles', function ($query) use ($roles) {
         return $query->whereIn('name', $roles);
    })->isNotEmpty();
}

Answer 2

我的建议是，使用关系加载用户的所有角色。当您通过将其称为属性来加载关系时，Laravel会将其缓存在引擎盖下，因此它不会重复任何查询。然后，您可以简单地使用加载的角色来实现两种方法：

public function hasAnyRoles(array $roles)
{
    // When you call $this->roles, the relationship is cached. Run through
    // each of the user's roles.
    foreach ($this->roles as $role) {
        // If the user's role we're looking at is in the provided $roles
        // array, then the user has at least one of them. Return true.
        if (in_array($role->name, $roles) {
            return true;
        }
    }

    // If we get here, the user does not have any of the required roles. 
    // Return false.
    return false;
}

和第二种方法：

public function hasRoles(array $roles)
{
    // Run through each of the roles provided, that the user MUST have
    foreach ($roles as $role) {
        // Call the $this->roles relationship, which will return a collection
        // and be cached. Find the first role that has the name of the role
        // we're looking at.
        $found = $this->roles->first(function ($r) use ($role) {
            return $r->name == $role;
        });

        // If a role could not be found in the user's roles that matches the
        // one we're looking, then the user does not have the role, return 
        // false
        if (!$found) {
            return false;
        }
    }

    // If we get here, the user has all of the roles provided to the method
    return true;
}

当然有许多不同的方法来实现这些方法，特别是Collection类中的方法对您有所帮助，但重点是使用$this->roles只会产生一个查询。

Laravel：检查关系中是否存在所有值

2 个答案: