Crystal JSON 处理示例

这个 demo 展示了如何使用 Crystal 的 JSON 模块处理 JSON 数据。

概念

Crystal 标准库提供了 JSON 模块，可以方便地解析和生成 JSON 数据。

main.cr

require "json"

# ===== 1. 解析 JSON 字符串 =====
puts "===== 1. 解析 JSON 字符串 ====="

json_str = <<-JSON
{
  "name": "Alice",
  "age": 30,
  "email": "alice@example.com",
  "skills": ["Nim", "Python", "Rust"],
  "address": {
    "city": "Beijing",
    "country": "China"
  },
  "active": true
}
JSON

parsed = JSON.parse(json_str)

puts "姓名: #{parsed["name"].as_s}"
puts "年龄: #{parsed["age"].as_i}"
puts "邮箱: #{parsed["email"].as_s}"
puts "技能: #{parsed["skills"].as_a.map(&.as_s)}"
puts "城市: #{parsed["address"]["city"].as_s}"
puts "活跃: #{parsed["active"].as_bool}"

# ===== 2. 构建 JSON 对象 =====
puts "\n===== 2. 构建 JSON 对象 ====="

user = JSON::Builder.new(IO::Memory.new)
user do
  object do
    field "name", "Bob"
    field "age", 25
    field "skills" do
      array do
        push "Go"
        push "Rust"
        push "C++"
      end
    end
    field "active", false
  end
end

puts "生成的 JSON:"
puts user.to_s

# ===== 3. JSON 映射到类 =====
puts "\n===== 3. JSON 映射到类 ====="

class Person
  include JSON::Serializable

  property name : String
  property age : Int32
  property email : String?
end

json_data = %({"name": "Carol", "age": 28, "email": "carol@example.com"})
person = Person.from_json(json_data)

puts "姓名: #{person.name}"
puts "年龄: #{person.age}"
puts "邮箱: #{person.email}"

# ===== 4. 复杂对象映射 =====
puts "\n===== 4. 复杂对象映射 ====="

class Address
  include JSON::Serializable

  property city : String
  property country : String
end

class Employee
  include JSON::Serializable

  property name : String
  property age : Int32
  property address : Address?
end

employee_json = <<-JSON
{
  "name": "David",
  "age": 35,
  "address": {
    "city": "Shanghai",
    "country": "China"
  }
}
JSON

employee = Employee.from_json(employee_json)

puts "员工: #{employee.name}"
puts "年龄: #{employee.age}"
puts "城市: #{employee.address.try &.city}"

# ===== 5. 数组处理 =====
puts "\n===== 5. 数组处理 ====="

numbers_json = "[1, 2, 3, 4, 5]"
numbers = JSON.parse(numbers_json).as_a

sum = 0
numbers.each do |n|
  sum += n.as_i
end

puts "数组: #{numbers.map(&.as_i)}"
puts "和: #{sum}"

# ===== 6. 类型安全的序列化 =====
puts "\n===== 6. 类型安全的序列化 ====="

class Config
  include JSON::Serializable

  property debug : Bool = false
  property timeout : Int32 = 30
  property servers : Array(String) = [] of String
end

config = Config.from_json(%({"debug": true, "timeout": 60, "servers": ["srv1", "srv2"]}))
config_json = config.to_json

puts "配置 JSON: #{config_json}"

# ===== 7. 处理嵌套数组 =====
puts "\n===== 7. 处理嵌套数组 ====="

matrix_json = "[[1,2,3],[4,5,6],[7,8,9]]"
matrix = JSON.parse(matrix_json).as_a

matrix.each_with_index do |row, i|
  row_arr = row.as_a
  puts "行 #{i}: #{row_arr.map(&.as_i).join(", ")}"
end