Understand instance_exec

Author: liijunwei

ruby/instance_exec_demo.rb

@@ -0,0 +1,22 @@
+class Demo
+  def foo(&block)
+    block.call
+  end
+
+  def bar(&block)
+    instance_exec(&block)
+  end
+end
+
+# rspec instance_exec_demo.rb
+RSpec.describe Demo do
+  context = self
+
+  let(:r1) { Demo.new.foo { self } }
+  let(:r2) { Demo.new.bar { self } }
+
+  it 'has different context' do
+    expect(r1).to be_a(context)
+    expect(r2).to be_a(Demo)
+  end
+end

ruby/my_factory_bot.rb

@@ -1,10 +1,14 @@
+require 'rspec'
+require 'pry'
+
 class User
   attr_accessor :name
   attr_accessor :email
 end
 
 class MyFactoryBot
-  def self.define
+  def self.define(&block)
+    instance_exec(&block)
   end
 
   def self.create(model_sym)
@@ -14,14 +18,12 @@ def self.create(model_sym)
 
 MyFactoryBot.define do
   factory :user do
+    require "pry"; binding.pry
     name { 'Bogs' }
     email { '[email protected]' }
   end
 end
 
-require 'rspec'
-require 'pry'
-
 # rspec my_factory_bot.rb
 RSpec.describe MyFactoryBot do
   describe '.create' do