Ruby检验变量

 

更新: 2017/06/12

更新: 2017/06/16 补充.class的输出

更新: 2017/06/23 .include?检验数组/哈希表是否包含目标值

更新: 2017/07/02 block_given?检验是否给了代码块以及检验是否有layout

更新: 2017/08/26 增加prensent?并与prensence比较

更新: 2018/01/03 增加is_a?, kind_of? (Object)

更新: 2018/02/03 增加instance_of?()的例子

更新: 2018/06/02 交换[instance_of?()] 和 [instance.class]的位置并修改相关标题，更方便查询

更新: 2018/10/12  增加frozen?, eql?, equal?

 

 检验是否定义

 defined? (sample)

返回值 str
未定义	nil
本地变量	local-variable
全局变量	global-variable
实例变量	instance-variable
类变量	class variable
常数	constant

 检验是否有值

 sample.nil?

 检验是否为空

 sample.empty?
 只对数组和哈希表可用

 rails可用
 empty? + nil?

 sample.blank?

 rails可用
 blank?的否定
 是否有值(+数组哈希表是否空)

 sample.presence

返回值

存在	不存在
self	nil

注意: 没有?
n. 出席; 仪表; 风度; 鬼魂，神灵;

 sample.present? 

 返回值

存在	不存在
true	false

 获取所属的类

instance.class

输出的是类，如Test等
 判断用  instance.class == Class

判断类

instance_of?(Object)

arr = Array.new(4, 1) # [1, 1, 1, 1]
arr.instance_of?(Array) # -> true

 判断类2 better

 is_a?, kind_of? (Object)
 和instance_of?的区别
   instance_of?只能判断自己当前的类
   is_a?,
kind_of?可以判断当前实例继承的类以及被包含的module

 检验是否包含目标 

 temp = [1, 2, 3]
 temp.include?(1)

不能用来比较哈希值

 是否给了代码块

 block_given?

 检验是否有layout

 content_for?(:sample) ? yield(:sample)
: yield

 检验是否冻结

 frozen?

 检验是否是指定的实例

 equal?

eql?

puts("----------------------------------------")

puts("    
     
     
 1.1")

puts("----------------------------------------")

asa = nil

asa = [1,2]

puts("asa#{asa}")

print("defined?: ", defined? asa);puts()

print("nil?: ", asa.nil?);puts()

print("empty?: ", asa.empty?);puts()

#print("blank?: ");print(asa.blank?);puts()

#print("presence?: ");print(asa.presence?);puts()

puts("----------------------------------------")

puts("    
     
     
 1.2")

puts("----------------------------------------")

local = 1

Const = 1

$global = 1

@instance = 1

@@class = 1

print("local: ", defined?(local));puts()

print("Const: ", defined?(Const));puts()

print("$global: ", defined?($global));puts()

print("@instance: ", defined?(@instance));puts()

print("@@class: ", defined?(@@class));puts()

 

puts("----------------------------------------")

puts("    
     
     
 1.3")

puts("----------------------------------------")

sample = []

print("isArray: ", sample.instance_of?(Array));puts();

print("class: ", sample.class);puts();

 

puts("----------------------------------------")

puts("    
     
     
 1.4")

puts("----------------------------------------")

#2017/06/16

class Test

  @a

  def initialize(num = 0)

    @a = num

  end

 

  def myFunc()

    puts(@a)

  end

end

sample = Test.new

p(sample.class)

p(sample.class.instance_of?(String))

p(sample.class.instance_of?(Test))

p(sample.class == Test)

 

puts("----------------------------------------")

puts("    
     
     
 1.5")

puts("----------------------------------------")

#2017/06/23

#include?

puts("array test: ")

temp = [1,2,3,5]

print(temp);puts();

for i in 1...5

  if temp.include?(i)

    printf("temp include
%d\n", i)

  else

    #printf("temp has no
member of %d\n", i)

    puts("temp has no member
of #{i}")

  end

end

 

puts("------------")

puts("hash test: ")

temp = {:a => 1, :b => 2, :c => 3, :d => 5}

temp1 = {x: 1, b: 2, c: 5, d: 7}

temp1.each_key do |item|

  if temp.include?(item)

    print("temp include %s",
item.inspect);puts();

  else

    puts("temp has no member
of #{item}")

  end

end

 

运行结果如下

----------------------------------------

1.1

----------------------------------------

asa[1, 2]

defined?: local-variable

nil?: false

empty?: false

----------------------------------------

1.2

----------------------------------------

check.rb:19: warning: class variable access from
toplevel

local: local-variable

Const: constant

$global: global-variable

@instance: instance-variable

check.rb:24: warning: class variable access from
toplevel

@@class: class variable

----------------------------------------

1.3

----------------------------------------

isArray: true

class: Array

----------------------------------------

1.4

----------------------------------------

Test

false

false

true

----------------------------------------

1.5

----------------------------------------

array test:

[1, 2, 3, 5]

temp include 1

temp include 2

temp include 3

temp has no member of 4

------------

hash test:

temp has no member of x

temp include :b

temp include :c

temp include :d