ruby - Ruby 函数的这两种实现有什么区别？

Question

1)

require 'sqlite3'

db = SQLite3::Database.new('development.sqlite3')
db.results_as_hash = true;


rows = db.execute(" SELECT * FROM listings WHERE name = '' OR telephone = '' OR latitude = '' OR longitude = '' ")

rows do |row|

  id_num = row['id']
  puts "Id = #{id_num}"

  dupe_name = row['name']
  puts "name = #{dupe_name}"

  dupe_tel = row['telephone']
  puts "tel = #{dupe_tel}"

  dupe_lat = row['latitude']
  puts "lat = #{dupe_lat}" 

  dupe_long = row['longitude']
  puts "lat = #{dupe_long}" 
  puts '===end===='



end

2)

    require 'sqlite3'

db = SQLite3::Database.new('development.sqlite3')
db.results_as_hash = true;


db.execute(" SELECT * FROM listings WHERE name = '' OR telephone = '' OR latitude = '' OR longitude = '' ") do |row|

  id_num = row['id']
  puts "Id = #{id_num}"

  dupe_name = row['name']
  puts "name = #{dupe_name}"

  dupe_tel = row['telephone']
  puts "tel = #{dupe_tel}"

  dupe_lat = row['latitude']
  puts "lat = #{dupe_lat}" 

  dupe_long = row['longitude']
  puts "lat = #{dupe_long}" 
  puts '===end===='



end

第二个有效，第一个无效。

为什么会这样呢？ db.execute 函数不返回结果集。如果是这样为什么你不能循环它？

Answer 1

您是否尝试过将第一个函数的 rows do |row| 更改为 rows.each do |row| ？

通过第一个，您将获得一个集合并将其分配给行。您需要为之后的行创建一个迭代器，以便循环遍历集合。

第二个函数，. execute已经返回一个迭代器。

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