Ruby History類用法及代碼示例

表示先前評估命令的結果曆史記錄。

通過 __ 變量可用，僅當 IRB.conf[:EVAL_HISTORY] 或 IRB::CurrentContext().eval_history 是非零整數值(默認為 nil )。

示例(在“irb”中)：

# Initialize history
IRB::CurrentContext().eval_history = 10
# => 10

# Perform some commands...
1 + 2
# => 3
puts 'x'
# x
# => nil
raise RuntimeError
# ...error raised

# Inspect history (format is "<item number> <evaluated value>":
__
# => 1 10
# 2 3
# 3 nil

__[1]
# => 10