发表新帖
发表新帖

GraphQL queries with tables join using Node.js

后端 未结
关注
2 1870
攒了一身酷
攒了一身酷 2021-02-01 14:52

I am learning GraphQL so I built a little project. Let\'s say I have 2 models, User and Comment.

const Comment = Model.defi
2条回答
  • -上瘾入骨i
    -上瘾入骨i (楼主)
    2021-02-01 15:20

    To anyone using .NET and the GraphQL for .NET package, I have made an extension method that converts the GraphQL Query into Entity Framework Includes.

    public static class ResolveFieldContextExtensions
{
    public static string GetIncludeString(this ResolveFieldContext source)
    {
        return string.Join(',', GetIncludePaths(source.FieldAst));
    }

    private static IEnumerable GetChildren(IHaveSelectionSet root)
    {
        return root.SelectionSet.Selections.Cast()
                                           .Where(x => x.SelectionSet.Selections.Any());
    }

    private static IEnumerable GetIncludePaths(IHaveSelectionSet root)
    {
        var q = new Queue>();
        foreach (var child in GetChildren(root))
            q.Enqueue(new Tuple(child.Name.ToPascalCase(), child));

        while (q.Any())
        {
            var node = q.Dequeue();
            var children = GetChildren(node.Item2).ToList();
            if (children.Any())
            {
                foreach (var child in children)
                    q.Enqueue(new Tuple
                                  (node.Item1 + "." + child.Name.ToPascalCase(), child));

            }
            else
            {
                yield return node.Item1;
            }
        }}}



    Lets say we have the following query: 
    


    query {
  getHistory {
    id
    product {
      id
      category {
        id
        subCategory {
          id
        }
        subAnything {
          id
        }
      }
    }
  }
}

    


    We can create a variable in "resolve" method of the field:
    


    var include = context.GetIncludeString();

    


    which generates the following string:
    


    "Product.Category.SubCategory,Product.Category.SubAnything"

    


    and pass it to Entity Framework:
    


    public Task Get(TKey id, string include)
{
    var query = Context.Set();
    if (!string.IsNullOrEmpty(include))
    {
        query = include.Split(',', StringSplitOptions.RemoveEmptyEntries)
                       .Aggregate(query, (q, p) => q.Include(p));
    }
    return query.SingleOrDefaultAsync(c => c.Id.Equals(id));
}

    
    
    
             
    
                                                        
    
            
            
    
              
                
                0
              
                   
                
               讨论(0)
              
                                                  
              
              
    
                          
             
       
          
              
    
                                       
    

    

                
    
                         
          
                              			
        
        
        
    
          
    
            
            
    
              
              
    
            
    


                                 
              
    
            
    
                          
    

        
         
    
                
                
    
                  
                
    
                
    
                   看不清?
                
    
              
    
                                  
    
                    
   
                 
             
              
    提交回复
    
            
    
          
    
        
    
      
       
      
    
    
    
          
 
     
 
    
        
    热议问题