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

def initialize(num = 0)

@a = num

end

def myFunc()

puts(@a)

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

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

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

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

巴特西

Ruby检验变量

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