ruby学习系列--Hash类函数
函数名称 | 说明 | 示例 |
== | 判断两个Hash是否相等 | h1 = {"a" => 1, "c" => 2} h2 = { "a" => 1, "c" => 2, 7 => 35 } h1 == h2 » false |
[ ] | 返回指定键值对应的对象 | h = { "a" => 100, "b" => 200 } h["a"] » 100 h["c"] » nil |
[ ]= | 向Hash添加记录 | h = { "a" => 100, "b" => 200 } h["a"] = 9 h["c"] = 4 h » {"a"=>9, "b"=>200, "c"=>4} |
clear | 清空哈希表的内容. 返回self. | h = { "a" => 100, "b" => 200 } h.clear » {} |
default | 返回哈希表的默认值 | h = { "a" => 100, "b" => 200 } h.default = "Go fish" h["a"] » 100 h["z"] » "Go fish" |
delete | 从词典中删除和键值相符的记录 | h = { "a" => 100, "b" => 200 } h.delete("a") » 100 h.delete("z") » nil h.delete("z") { |el| "#{el} not found" } »"z not found" |
delete_if | 通过过程块来删除特定键值的记录 | h = { "a" => 100, "b" => 200 } h.delete_if {|key, value| key >= "b" } » {"a"=>100} |
each | Hash表的迭代操作，对表的每一个词对进行迭代操作 | h = { "a" => 100} h.each {|key, value| print key, " is ",value,""n"} » a is 100 |
each_key | 对表的每一个键对进行迭代操作 | h = { "a" => 100, "b" => 200 } h.each_key {|key| print key } » ab |
each_value | 针对value进行迭代操作 | h = { "a" => 100, "b" => 200 } h.each_value {|value| print value } » 100200 |
empty? | 判断哈希表是否为空，空则返回true | {}.empty? » true |
fetch | 如果能找到键值为key的hash值，则返回Hash值； 如果找不到，则返回默认值或指定值； 如果默认值和指定值都找不到，抛异常 | h = { "a" => 100, "b" => 200 } h.fetch("a") » 100 h.fetch("z", "go fish") » "go fish" h.fetch("k") »in `fetch': key not found (IndexError) |
has_key? | 判断是否存在相符的key值 | h = { "a" => 100, "b" => 200 } h.has_key?("a") » true h.has_key?("z") » false |
key？ | h. key?("z") » false | |
include? | h.include?("b") » true | |
has_value? | 判断是否存在相符的value值 | h = { "a" => 100, "b" => 200 } h.has_value?(100) » true h.has_value?(999) » false |
value? | h.value?(100) » true h.value?(999) » false | |
index | 返回给定值的键值，未找到返nil | h = { "a" => 100, "b" => 200 } h.index(200) » "b" h.index(999) » nil |
indexes | 返回一系列给定的键值对应值组成的数组 | h = { "a" =>100, "b" =>200, "c" =>300 } h.indexes("a", "c") » [100,300] h.indexes("a","z") » [100,nil] |
indices | h.indexes("a", "c") » [100,300] h.indexes("a", "z") » [100,nil] | |
invert | 将元素值和索引互换,返回变换后的哈希表. 注意:若原哈希表中若干不同的索引对应相同的元素值时,其变换结果将无法预测. | h = { "n" => 100,"m" => 100,"y" => 300} h.invert » {300=>"y",100=>"n"} |
keys | 返回一个包含所有key的数组. | h = { "a" => 100, "b" => 200 } h.keys » ["a", "b"] |
values | 返回一个包含所有vakue的数组. | h = { "a" => 100,"b" => 200,"c" => 300 } h.values » [100, 200, 300] |
length | 返回词典中元素的个数 | h = { "d" =>100, "a"=> 200, "v" => 300} h.length » 3 h. size » 3 |
size | ||
rehash | 重新计算索引对应的哈希表值。 当与索引对应的哈希表值发生变化时，若不使用该方法来重新计算的话，将无法取出与索引对应的哈希表值。 | a = [ "a", "b" ] c = [ "c", "d" ] h = { a => 100, c => 300 } a[0] = "z" h.rehash » {["z", "b"]=>100, ["c", "d"]=>300} h[a] » 100 |
replace | 以另外一张Hash表的内容来替换当前Hash表的内容 | h = {"a" =>100, "b" =>200 } h.replace({ "c" => 300, "d" => 400 }) » {"c"=>300, "d"=>400} |
shift | 删除一个哈希表元素后 再以[key,value]数组的形式将其返回 | h = { 1 => "a", 2 => "b", 3 => "c" } h.shift » [1, "a"] h » {2=>"b", 3=>"c"} |
sort | 对Hash进行排序 按键值从小到大排序 | h = { "b" => 30, "a" => 20, "c" => 10 } h.sort » [["a", 20], ["b", 30], ["c", 10]] h.sort {|a,b| a[1]<=>b[1]} » [["c", 10], ["a", 20], ["b", 30]] |
to_a | 把Hash表转换为数组 数组按Hash表的键值从小到大排序 | h = {"c" =>300,"a" =>100,"d" =>400} » [["a", 100], ["c", 300], ["d", 400]] |
to_s | 把Hash表转换为字符串 | h = { "c" => 300, "a" => 100, "d" => 400} h.to_s » "a100c300d400" |
update | 用一张Hash表去更新另外张Hash表 | h1 = { "a" => 100, "b" => 200 } h2 = { "b" => 254, "c" => 300 } h1.update(h2) » {"a"=>100, "b"=>254, "c"=>300} |