nim-lang - 这是使用 Nim ref 数据结构的有效方法吗？

Question

我在记忆中保留了大量公司，并且需要做大量的操作来获得单个公司。

就像通过其符号“MSFT”获得个别公司“Microsoft”。

下面的数据结构是否是对其建模的正确方法？list整个or不应该有按值复制map。

可以按价值复制个别公司。

import tables

type
  Company = object
    name:        string
    symbol:      string
    description: string

  CompaniesRef = ref object
    list: seq[Company]
    map:  Table[string, Company]

# Cached data structure to keep thousands of different companies
var cached_companies: CompaniesRef
proc companies(): CompaniesRef =
  if cached_companies == nil:
    # Here will be a proper code of loading companies into the 
    # CompaniesRef data structure
    cached_companies = CompaniesRef()
  cached_companies

# Lots of operations of getting a specific company from the list
# or from the map by its symbol
for i in 1..1000:
  # it's ok if individual company will be copied by value,
  # but the whole list should be passed by reference
  let company1 = companies().list[0].name

  # it's ok if individual company will be copied by value
  # but the whole map should be passed by reference
  let company2 = companies().map["MSFT"]

标签： nim-lang

Answer 1

该全局结构应该没问题，对象引用只是一个内存管理指针，因此传递它的引用只会复制内存地址。除非你打算用那个指针做点什么，否则为什么不把它创建为一个全局的呢？将其隐藏在 proc 调用后面会散发出I'm-afraid-of-globals-but-can't-live-without-them-singleton模式的味道。

let companies = CompaniesRef()

关于结构的内容，您要存储每个对象两次，如果您需要保持插入键的顺序Company，您可能希望存储对Companyin 的引用Table或简单地使用OrderedTable 。