cc.expect

The cc.expect library provides helper functions for verifying that function arguments are well-formed and of the correct type.

Usage

• Define a basic function and check it has the correct arguments.

  local expect = require "cc.expect"
  local expect, field = expect.expect, expect.field
  
  local function add_person(name, info)
      expect(1, name, "string")
      expect(2, info, "table", "nil")
  
      if info then
          print("Got age=", field(info, "age", "number"))
          print("Got gender=", field(info, "gender", "string", "nil"))
      end
  end
  
  add_person("Anastazja") -- `info' is optional
  add_person("Kion", { age = 23 }) -- `gender' is optional
  add_person("Caoimhin", { age = 23, gender = true }) -- error!

Changes

• New in version 1.84.0
• Changed in version 1.96.0: The module can now be called directly as a function, which wraps around expect.expect.

expect(index, value, ...)Source

Expect an argument to have a specific type.

Parameters

1. index number The 1-based argument index.
2. value The argument's value.
3. ... string The allowed types of the argument.

Returns

1. The given value.

Throws

• If the value is not one of the allowed types.

field(tbl, index, ...)Source

Expect an field to have a specific type.

Parameters

1. tbl table The table to index.
2. index string The field name to check.
3. ... string The allowed types of the argument.

Returns

1. The contents of the given field.

Throws

• If the field is not one of the allowed types.

range(num, min, max)Source

Expect a number to be within a specific range.

Parameters

1. num number The value to check.
2. min number The minimum value, if nil then -math.huge is used.
3. max number The maximum value, if nil then math.huge is used.

Returns

1. The given value.

Throws

• If the value is outside of the allowed range.

Changes

• New in version 1.96.0