JavaScript的Function.prototype.bind是否有Ruby等价物？

Question

JavaScript的快乐时光乐趣土地

// make a method 
var happy = function(a, b, c) { 
    console.log(a, b, c); 
}; 

// store method to variable 
var b = happy; 

// bind a context and some arguments 
b.bind(happy, 1, 2, 3); 

// call the method without additional arguments 
b(); 

输出。好极了！

1 2 3 

---

在Ruby

# make a method 
def sad a, b, c 
    puts a, b, c 
end 

# store method to variable 
b = method(:sad) 

# i need some way to bind args now 
# (this line is an example of what i need) 
b.bind(1, 2, 3) 

# call the method without passing additional args 
b.call 

所需的输出

1, 2, 3 

---

对于它的价值，我知道JavaScript可以改变的第一个参数的结合上下文传递给.bind。在Ruby中，即使我无法更改上下文，我也会很开心。我主要需要简单地将参数绑定到方法。

问题

是否有参数绑定到一个Ruby Method的实例，例如，当我打电话method.call没有额外的参数，被绑定参数是仍然传递给方法的方法吗？

目标

这是一个常见的JavaScript的成语，我认为这将是任何语言有用。目标是将方法M传递给接收方R，其中R不需要（或具有）当R执行该方法时要将哪些（或多少）参数发送给M的固有知识。这如何可能是有用的

/* this is our receiver "R" */ 
var idiot = function(fn) { 
    console.log("yes, master;", fn()); 
}; 


/* here's a couple method "M" examples */ 
var calculateSomethingDifficult = function(a, b) { 
    return "the sum is " + (a + b); 
}; 

var applyJam = function() { 
    return "adding jam to " + this.name; 
}; 

var Item = function Item(name) { 
    this.name = name; 
}; 


/* here's how we might use it */ 
idiot(calculateSomethingDifficult.bind(null, 1, 1)); 
// => yes master; the sum is 2 

idiot(applyJam.bind(new Item("toast"))); 
// => yes master; adding jam to toast 

Answer 1

通常

一个JavaScript示范，重新绑定方法是不是你在Ruby中做一些事情。相反，您可以使用块：

# This is our receiver "R" 
def idiot(&block) 
    puts("yes, master; #{block.call}") 
end 


# Here's a couple method "M" examples 
def calculateSomethingDifficult(a, b) 
    return "the sum is #{a + b}" 
end 

def applyJam(object) 
    return "adding jam to " + object.name 
end 

class Item 
    attr_reader :name 
    def initialize(name) 
    @name = name 
    end 
end 


# Here's how we might use it 
idiot do 
    calculateSomethingDifficult(1, 1) 
end 
#=> yes master; the sum is 2 

# You *can* change calling context too (see instance_exec), but I'd 
# discourage it. It's probably better to just pass the object as a 
# parameter. 
idiot do 
    applyJam(Item.new("toast")) 
end 
#=> yes master; adding jam to toast 

---

如果你真的想“绑定”的方法，如你在JavaScript这样做是绝对有可能，但：

class Method 
    def bind *args 
    Proc.new do |*more| 
     self.call *(args + more) 
    end 
    end 
end 

这应该使你的榜样工作几乎正如你最初描述的那样：

# make a method 
def sad a, b, c 
    puts a, b, c 
end 

# store method to variable 
b = method(:sad) 

# Get a "bound" version of the method 
b = b.bind(1, 2, 3) 

# call the method without passing additional args 
b.call 

如果你需要它确切的，你可以定义Object#bindable_method返回一些你想要的BindableMethod类。尽管我认为大多数情况下上述都适合你。

Answer 2

Proc#curry Ruby中类似于JavaScript中的bind。

def happy(a, b, c, d = 100) 
    puts a, b, c, d 
end 

proc = method(:happy).to_proc.curry # proc is now a curried Proc 

b = proc.call(1,2) # b is a curried Proc with 1 and 2 bound as the first arguments 

b.call(3) # Call the proc, providing the 3rd argument 

不能完全复制你的示例代码，因为当咖喱PROC被称为所需的参数，它返回PROC的结果---换句话说，你不能约束所有的参数和然后再调用proc ---你必须至少保留一个参数。

这不一定比Ajedi32提供的代码一个更好的选择，但我认为这是值得一提，因为它的内置到Ruby。

看到文档在这里：http://ruby-doc.org/core-2.2.0/Proc.html#method-i-curry