1.Kernel#eval
2.0.0p247 :428 > array = ['10','20']
=> ["10", "20"]
2.0.0p247 :429 > element = '30'
=> "30"
2.0.0p247 :430 > eval('array << element')
=> ["10", "20", "30"]
2.0.0p247 :431 >
对比方法与块
.0.0p247 :422 > array = ['a','b','c
2.0.0p247 :423'> ']
=> ["a", "b", "c\n"]
2.0.0p247 :424 > x = 'abc'
=> "abc"
2.0.0p247 :425 > array.instance_eval "self[1] = x"
=> "abc"
2.0.0p247 :426 > array
=> ["a", "abc", "c......
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