ruby - How do I change the context of lambda? -


if run code below error.

class c   def self.filter_clause param_1     puts param_1     yield # context of param class b   end    def hi     "hello"   end end  class b   def self.filter(value, lambda)     code = lambda { filter_clause(value, &lambda) }     c.instance_exec(&code)   end    filter(:name, ->{ hi }) end

the error 

nameerror: undefined local variable or method `hi' b:class (pry):17:in `block in <class:b>'

from understanding reason lambda running under context of class b. can't find method def hi. can't figure out how run under context of class c.

essentially want able inject method being called in class accepts argument , block.

for example:

filter_clause("value", ->{ hi })

is possible?

not sure if making sense.

you're close. if want lambda(/block, really) execute in context of instance of c (since hi instance method on c), you'll need instantiate , instance_exec block on new instance:

class c   def self.filter_clause param_1, &block     puts new.instance_exec &block   end    def hi     "hello"   end end  class b   def self.filter(value, lambda)     code = lambda { filter_clause(value, &lambda) }     c.instance_exec(&code)   end    filter(:name, ->{ hi }) end  # => hello

Comments

Post a Comment

Popular posts from this blog

javascript - Google App Script ContentService downloadAsFile not working -

i have web app developed using google app script htmlservice , html form, populating excel sheet in google drive using spreadsheetapp . , 1 section calling contentservice download data excel file. function doget(e) { // read excel sheet //getappfile(); // render application html template return htmlservice.createtemplatefromfile('index').evaluate() .settitle('go smart') .setsandboxmode(htmlservice.sandboxmode.iframe); } function downloaddoublequatecsvfile() { var sheetid = propertiesservice.getscriptproperties().getproperty('sheetid'); var ss = spreadsheetapp.openbyid(sheetid).getactivesheet(); //var ss = spreadsheetapp.getactivespreadsheet().getactivesheet(); var maxcolumn = ss.getlastcolumn(); var maxrow = ss.getlastrow(); var data = ss.getrange(1, 1, maxrow, maxcolumn).getvalues(); if (data.length > 1) { var csv = ""; (var row = 0; row < data.length; row++) { (var c...
Read more

javascript - Function overwritting -

is there way overwrite function or event handling in function? using addeventlistener, can have many event handlers on element want var test=document.getelementbyid("div"); test.addeventlistener("click",function(){alert("im first");},false); test.addeventlistener("click",function(){alert("im second");},false); // alerts "im first" , after "im second" but if want overwrite function/event example based on client width example this function one() { alert("first"); } function two() { alert("second"); } window.onresize = function() { var test = document.getelementbyid("div"); if (window.innerwidth > 500) { test.onclick = 1 } else { test.onclick = two; } } is possible in javascript? in case use effective little known approach. addeventlistener can accept object property handleevent event handler. in case it's easy overwr...
Read more

c# - Exception when attempting to modify Dictionary -

i creating dictionary manage threads , ran exception when attempt clear dead threads after adding threads dictionary. using system; using system.collections.generic; using system.threading; namespace syscat { public class threadmanager { public static readonly threadmanager globalthreadmanager = new threadmanager( ); /// <summary> /// initializes new instance of <see cref="syscat.threadmanager"/> class. /// </summary> public threadmanager( ) { } /// <summary> /// create new threadmanager threads within basetm , deinitializes basetm /// </summary> public threadmanager( threadmanager basetm ) { this.threads = basetm.threads; basetm.threads.clear( ); } private dictionary<guid,thread> threads = new dictionary<guid, thread>( ); /// <summary> /// attempts obtain unused threadid within ...
Read more