從`object.method`發送一個方法字符串

Question

我想在來自不同來源的數據塊中運行同一個進程。我從中獲取要搜索的元素的方法具有不同的名稱。這是我想要做的一個例子：

def search_in(list, i) 
    send(list) { |s| puts s if s.include?(i) } 
end 

然後，我想叫它像下面這樣：

search_in("contents.each", i)或search_in("@things.entries", i)

Answer 1

send只是發送消息（方法調用）一個接收器。你指定接收器作爲字符串的一部分，這意味着你必須做一些巫術來正確提取它。不過，你可能正在做一些你不應該在這裏的事情 - 我鼓勵你詳細說明你的問題，以獲得有關如何重構它以避免此特定操作的建議。

但是，要解決這個問題，您需要提取並解析接收者，提取消息，然後將消息發送給接收者。你應該避免評估。

給定一個字符串，list

# Split the string into something that should resolve to the receiver, and the method to send 
receiver_str, method = list.split(".", 2) 

# Look up possible receivers by looking in instance_methods and instance_variables. 
# Note that this isn't doing any constant resolution or anything; the assumption 
# is that the receiver is visible in the current scope. 
if instance_methods.include?(receiver_str) 
    receiver = send(receiver_str) 
elsif instance_variables.include?(receiver_str) 
    receiver = instance_variable_get(receiver_str) 
else 
    raise "Bad receiver: #{receiver_str}" 
end 

receiver.send(method) {|s| ... } 

考慮到這是一個靜態塊，雖然，你期望一個可枚舉傳遞;而不是傳遞字符串來解析爲接收方和方法，您應該嘗試通過Enumerable本身：

def search_enumerable_for(enum, i) 
    enum.each {|e| puts e if e.include?(i) } 
end 

search_enumerable_for(contents, value) 
search_enumerable_for(@things.entries, value)