Ruby 数组（Array）
一、参数= 符号赋值数组对象 时，是指向同一个数组对象https://i-blog.csdnimg.cn/direct/860cf495ccf94605a6e191ab49e9e28d.png
eg:
irb(main):019:0> a = [] //定义一个数组
=> []
irb(main):020:0> b = a //将变量a赋值给b，a和b指向同个内存
=> []
irb(main):021:0> a.object_id//a的对象id
=> 25204596
irb(main):022:0> b.object_id//b的对象id
=> 25204596
irb(main):023:0> a << 'foo'//a写入值foo
=> ["foo"]
irb(main):024:0> b// 打印b的值发现和a一样
=> ["foo"]
二、界说数组的方法
1.[] 界说数组
irb(main):025:0> a = ['1','2']
=> ["1", "2"] 2.Array.new():括号中可以输入界说数组的长度，和数组的相同值，修改其中一个，其他值都改变，数组的参数都指向同一个对象
irb(main):026:0> Array.new(3)//定义一个长度为3个的无数据的数组
=>
irb(main):027:0> Array.new(3,"asdf") //定义有3个asdf 字符的数组
=> ["asdf", "asdf", "asdf"]
irb(main):028:0> b =Array.new(3,"asdf")//定义有3个asdf 字符的数组并赋值给b
=> ["asdf", "asdf", "asdf"]
irb(main):029:0> b//b数组的第一参数的值
=> "asdf"
irb(main):030:0> b//b数组的第二参数的值
=> "asdf"
irb(main):031:0> b.object_id //b数组的第一参数对象的值
=> 25986720
irb(main):032:0> b.object_id //b数组的第二参数对象的值
=> 25986720
irb(main):033:0> b='m'//b数组的第二数据asdf 第三个字符d 改为m
=> "m"
irb(main):034:0> b
=> "asmf"
irb(main):035:0> b
=> "asmf"
irb(main):036:0> b
=> "asmf"
3.Array.new(){}:创建多个数组，值不一样，修改后不会都修改，可以修改指定值
irb(main):038:0> c = Array.new(2){'abcd'} //定义一个数组大小为2个，值都为abcd 的不同对象
=> ["abcd", "abcd"]
irb(main):039:0> c //查看数组第一个的值
=> "abcd"
irb(main):040:0> c//查看数组第二个的值
=> "abcd"
irb(main):041:0> c.object_id//查看数组第一个值的对象id
=> 25344288
irb(main):042:0> c.object_id //查看数组第二个值的对象id
=> 25344276
irb(main):043:0> c='k'//查看数组第二个值的字符串的第三个字符设置为k
=> "k"
irb(main):044:0> c//查看数组第一个的值
=> "abcd"
irb(main):045:0> c//查看数组第二个的值，可以看到只有第二个值改变了
=> "abkd" 3. %w(): 简朴快速的界说数组，不必要输入单引号和逗号
irb(main):046:0> arr = %w(aa bb cc dd)
=> ["aa", "bb", "cc", "dd"] 三、数组的方法
1.[]：查看第几个数据
irb(main):048:0> a = %w(foo bar wut wat) //定义数组
=> ["foo", "bar", "wut", "wat"]
irb(main):049:0> a //获取数组的第一个数据
=> "foo"
2.[..]：查看区间数据
irb(main):050:0> a[-1] //获取最后一个
=> "wat"
irb(main):051:0> a
=> ["bar", "wut"]
3.fetch():安全的取数据，可以界说取不到数据的情况
irb(main):052:0> a.fetch(2)
=> "wut"
irb(main):053:0> a.fetch(4)
IndexError: index 4 outside of array bounds: -4...4
from (irb):53:in `fetch'
from (irb):53
from D:/RailsInstaller/Ruby2.2.0/bin/irb:11:in `<main>'
irb(main):054:0> a.fetch(4,'asdf')
=> "asdf" 4.length
irb(main):055:0> a.length
=> 4 5.include?():数组是否包罗哪些字符
irb(main):057:0> a.include?('foo')
=> true
irb(main):058:0> a.include?('aa')
=> false 6.empty?(): 是否为空数组
irb(main):059:0> a.empty?()
=> false 7.push():往数组后添加数据,也可以添加相同值
irb(main):060:0> a.push('haha')
=> ["foo", "bar", "wut", "wat", "haha"] 8.[]=:数组指定位置添加数据，如果中心没有数据，会创建空数据
irb(main):061:0> a='aab'
=> "aab"
irb(main):062:0> a
=> ["foo", "bar", "wut", "wat", "haha", nil, nil, nil, nil, nil, "aab"] 9.delete_at():删除指定位置的值
irb(main):062:0> a
=> ["foo", "bar", "wut", "wat", "haha", nil, nil, nil, nil, nil, "aab"]
irb(main):063:0> a.delete_at(0)
=> "foo"
irb(main):064:0> a
=> ["bar", "wut", "wat", "haha", nil, nil, nil, nil, nil, "aab"] 10.delete():删除指定内容的值
irb(main):064:0> a
=> ["bar", "wut", "wat", "haha", nil, nil, nil, nil, nil, "aab"]
irb(main):065:0> a.delete('haha')
=> "haha"
irb(main):066:0> a
=> ["bar", "wut", "wat", nil, nil, nil, nil, nil, "aab"] 11.uniq!: 相同值删除，保存其中一个,不加感叹号
irb(main):067:0> a.push('bar')
=> ["bar", "wut", "wat", nil, nil, nil, nil, nil, "aab", "bar"]
irb(main):068:0> a.uniq()
=> ["bar", "wut", "wat", nil, "aab"] 12.shuffe: 将数组数据随机排序
irb(main):072:0> a.shuffle
=> ["bar", "wut", "aab", "wat", nil]
irb(main):073:0> a
=> ["bar", "wut", "wat", nil, "aab"] 13.falttern:二维数组转为1维数组
irb(main):001:0> a=[,['a','b','c']]//创建二维数组
=> [, ["a", "b", "c"]]
irb(main):002:0> a.flatten//将二维数组转为一维数组
=> 四、遍历数组
1.each{}:遍历数组
irb(main):004:0> arr=['a','b','c','d'] //创建arr数组
=> ["a", "b", "c", "d"]
irb(main):006:0> arr.each{|e| p e} //遍历打印数组，eg |e|为变量ep为打印的意思 e为变量
"a"
"b"
"c"
"d"
=> ["a", "b", "c", "d"] 2.reverse_each{}: 倒序遍历数组
irb(main):004:0> arr=['a','b','c','d']
=> ["a", "b", "c", "d"]
irb(main):007:0> arr.reverse_each{|e| p e} //倒序打印arr数组
"d"
"c"
"b"
"a"
=> ["a", "b", "c", "d"] 3.each_with_index: 下标遍历数组
irb(main):001:0> arr=['a','b','c','d']
=> ["a", "b", "c", "d"]
irb(main):002:0> arr.each_with_index{|e,i| p } //定义e和i变量，e为数组数据，i为数组的下标
["a", 0]
["b", 1]
["c", 2]
["d", 3]
=> ["a", "b", "c", "d"]
4.sort:数组数据从小到大排序
irb(main):003:0> arr=[-1,-2,-4,0,99,-2,8]
=> [-1, -2, -4, 0, 99, -2, 8]
irb(main):004:0> arr.sort
=> [-4, -2, -2, -1, 0, 8, 99] 5.select{}:遍历判定数组的值
irb(main):003:0> arr=[-1,-2,-4,0,99,-2,8]
=> [-1, -2, -4, 0, 99, -2, 8]
irb(main):005:0> arr.select{|e| e>0}//数组元素大于0的数据
=> 6.compact: 删除数组里面空元素
irb(main):006:0> arr<< nil
=> [-1, -2, -4, 0, 99, -2, 8, nil]
irb(main):007:0> arr.compact//删除nil 空白元素，ps要想对arr生效，可以用危险！eg:arr.compact!
=> [-1, -2, -4, 0, 99, -2, 8]
irb(main):008:0> arr
=> [-1, -2, -4, 0, 99, -2, 8, nil]
irb(main):009:0> arr.compact!
=> [-1, -2, -4, 0, 99, -2, 8]
irb(main):010:0> arr
=> [-1, -2, -4, 0, 99, -2, 8] 7.any?{}: 是否含有{条件}。eg：是否含有小于 零的数
irb(main):010:0> arr
=> [-1, -2, -4, 0, 99, -2, 8]
irb(main):011:0> arr.any?{|e| e<0}//数组是否含有小于0的元素
=> true 更多array利用：https://ruby-doc.org//core-2.2.0/Array.html
课后训练
输入：input= 输出：output =
要求：
不能改变原input
output 是一个新的array object
尽量简便
output= []
input.each{|e| output << e*2}
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