尝试解析一些 JSON，为什么 text 是空的？

期望的输出:

text 应该返回 Hello world\n\nApple, Harbor\n\nBanana, Kitchen\n\nMango, Bedroom

text = "Hello world"

json = '{"fruits": [{"name": "Apple", "location": "Harbor"}, {"name": "Banana", "location": "Kitchen"}, {"name": "Mango", "location": "Bedroom"}]}'
fruits = JSON.parse(json)

def format_fruits(fruits)
  fruits.each do |fruit|
    puts "\n\n#{ fruit[0]['name'] }, #{ fruit[0]['location'] }"
  end.to_sentence
end

text += format_fruits(fruits)
text

当前输出:

TypeError: no implicit conversion of Hash into String
        from (irb):5:in `+'
        from (irb):5
        from /home/mark/.gem/ruby/2.1.1/gems/railties-4.1.7/lib/rails/commands/console.rb:90:in `start'
        from /home/mark/.gem/ruby/2.1.1/gems/railties-4.1.7/lib/rails/commands/console.rb:9:in `start'
        from /home/mark/.gem/ruby/2.1.1/gems/railties-4.1.7/lib/rails/commands/commands_tasks.rb:69:in `console'
        from /home/mark/.gem/ruby/2.1.1/gems/railties-4.1.7/lib/rails/commands/commands_tasks.rb:40:in `run_command!'
        from /home/mark/.gem/ruby/2.1.1/gems/railties-4.1.7/lib/rails/commands.rb:17:in `<top (required)>'
        from /home/mark/.gem/ruby/2.1.1/gems/activesupport-4.1.7/lib/active_support/dependencies.rb:247:in `require'
        from /home/mark/.gem/ruby/2.1.1/gems/activesupport-4.1.7/lib/active_support/dependencies.rb:247:in `block in require'
        from /home/mark/.gem/ruby/2.1.1/gems/activesupport-4.1.7/lib/active_support/dependencies.rb:232:in `load_dependency'
        from /home/mark/.gem/ruby/2.1.1/gems/activesupport-4.1.7/lib/active_support/dependencies.rb:247:in `require'
        from /home/mark/myapp/bin/rails:8:in `<top (required)>'
        from /home/mark/.gem/ruby/2.1.1/gems/activesupport-4.1.7/lib/active_support/dependencies.rb:241:in `load'
        from /home/mark/.gem/ruby/2.1.1/gems/activesupport-4.1.7/lib/active_support/dependencies.rb:241:in `block in load'
        from /home/mark/.gem/ruby/2.1.1/gems/activesupport-4.1.7/lib/active_support/dependencies.rb:232:in `load_dependency'
        from /home/mark/.gem/ruby/2.1.1/gems/activesupport-4.1.7/lib/active_support/dependencies.rb:241:in `load'
        from /home/mark/.gem/ruby/2.1.1/gems/spring-1.1.3/lib/spring/commands/rails.rb:6:in `call'
        from /home/mark/.gem/ruby/2.1.1/gems/spring-1.1.3/lib/spring/command_wrapper.rb:38:in `call'
        from /home/mark/.gem/ruby/2.1.1/gems/spring-1.1.3/lib/spring/application.rb:180:in `block in serve'
        from /home/mark/.gem/ruby/2.1.1/gems/spring-1.1.3/lib/spring/application.rb:153:in `fork'
        from /home/mark/.gem/ruby/2.1.1/gems/spring-1.1.3/lib/spring/application.rb:153:in `serve'
        from /home/mark/.gem/ruby/2.1.1/gems/spring-1.1.3/lib/spring/application.rb:128:in `block in run'
        from /home/mark/.gem/ruby/2.1.1/gems/spring-1.1.3/lib/spring/application.rb:122:in `loop'
        from /home/mark/.gem/ruby/2.1.1/gems/spring-1.1.3/lib/spring/application.rb:122:in `run'
        from /home/mark/.gem/ruby/2.1.1/gems/spring-1.1.3/lib/spring/application/boot.rb:18:in `<top (required)>'
        from /home/mark/.rubies/ruby-2.1.1/lib/ruby/2.1.0/rubygems/core_ext/kernel_require.rb:55:in `require'
        from /home/mark/.rubies/ruby-2.1.1/lib/ruby/2.1.0/rubygems/core_ext/kernel_require.rb:55:in `require'
        from -e:1:in `<main>'irb(main):006:0> text
=> "Hello world"
irb(main):007:0>

最佳答案

错误是调用 Array#to_sentence 的结果在散列上。

更具体地说，fruits 是一个Hash，调用fruits.each { ... } 返回原始的fruits Hash 不变。因此调用 fruits.to_sentence 会导致观察到的错误。

这是一个修正后的版本，带有表示更改的注释:

require 'json'

text = "Hello world"

json = '{"fruits": [{"name": "Apple", "location": "Harbor"}, {"name": "Banana", "location": "Kitchen"}, {"name": "Mango", "location": "Bedroom"}]}'
fruits = JSON.parse(json)['fruits'] # append ['fruits']

def format_fruits(fruits)
  fruits.map do |fruit| # change each -> map
    "\n\n#{ fruit['name'] }, #{ fruit['location'] }" # delete puts, [0]
  end.join # change to_sentence -> join
end

text += format_fruits(fruits)
puts text

输出:

Hello world

Apple, Harbor

Banana, Kitchen

Mango, Bedroom

关于 ruby - 类型错误 : no implicit conversion of Hash into String，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/27372255/