hash1 = {:one=>1,:two=>2}
hash2 = {:two=>2,:one=>1}
hash1 == hash2
=> true
assert_equal hash1, hash2
=> true
hash1.object_id == hash2.object_id
=> false这个情况下hash1和hash2明显不是同一个对象为什么可以assert_equal?
hash = { "jim" => 53, "amy" => 20, "dan" => 23 }
new_hash = hash.merge({ "jim" => 54, "jenny" => 26 })
expected = { "jim" => 53, "amy" => 20, "dan" => 23, "jenny" => 26 }
expected == new_hash
=> false这个情况下为什么expected和new_hash又不等了？
还有一个，求大神解释一下：
hash = Hash.new {|hash, key| hash[key] = [] }这句话是什么意思？这个语法是怎么回事？三个hash一样么？
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1,
Hash#==方法, 当两个哈希有相同数目的键值对, 且键值对根据自身的#==method determines equality, then the two hashes are equalDescription:
:one=>1就是键值对,:one为符号, 为键,1为整数, 为值. Ruby中的符号是全局唯一的, 即:one就只有一个, 自然彼此相等,1is an integer, and the equality judgment is also very intuitive.Ruby’s judgment is pending,
#==方法会被子类覆盖, 提供语义的相等, 如1==1.0为true. 而#equal?禁止覆盖, 比较对象的#object_id, 即只有同一个对象才equal, 如1.equal? 1.0为false. 题主应该说的是#equal?.2, the value of
Hash#merge方法, 如h1.merge h2, 对于相同的键,h1会被h2中覆盖. 即new_hash["jim"]为54. 你可以让h2 merge h1, 如果你想要h1. Or, as follows3,
Hash.new主要处理的是, 当索引不存在的键时, 哈希应该返回什么值, 如hash1['not_exist_key']. 此处,|hash, key|中,hash即为hash1, 即调用对象,key为'not_exist_key'. 此语句的意思是, 当索引不存在的键时, 返回空数组[], 更简单的写法是hash = Hash.new([]).expected and new_hash are not equal because one jim is 53 and the other jim is 54!