I am currently having a list of obeject defined as:
fun updateList(tools: List<Tool>, updateTools: List<Updated>){
... code below
}
the Tool data class is defined as:
data class Tool(
var id: String = ""
var description: String = ""
var assignedTo: String = ""
)
the Updated data class is defined as:
data class Updated(
var id: String = ""
var assignedTo: String = ""
)
Basically, I parse the list updateTools and if I found a id match in tools, I update the assignedTo field from the Tool type object from tools by the one from updateTools
fun updateList(tools: List<Tool>, updateTools: List<Updated>){
updateTools.forEach{
val idToSearch = it.id
val nameToReplace = it.name
tools.find(){
if(it.id == idToSearch){it.name=nameToReplace}
}
}
return tools
}
it's not working but I do not see how to make it easier to work. I just started kotlin and I feel that it's not the good way to do it
any idea ?
Thanks
First of all:
you're not assigning assignedTo, you're assigning name...
in the predicate passed to find, which
should only return a Boolean value to filter elements, and
should probably not have any side effects,
those should be done later with a call to i.e. forEach.
Additionally, your constructor parameters to the data class are normal parameters, and as such, need commas between them!
Your last code block, corrected, would be:
updateTools.forEach {
val idToSearch = it.id
val nameToReplace = it.name
tools.find { it.id == idToSearch }.forEach { it.assignedTo = nameToReplace }
}
return tools
I'd do it like this (shorter):
updateTools.forEach { u -> tools.filter { it.id == u.id }.forEach { it.assignedTo = u.name } }
This loops through each update, filters tools for tools with the right ID, and sets the name of each of these tools.
I use forEach as filter returns a List<Tool>.
If you can guarantee that id is unique, you can do it like this instead:
updateTools.forEach { u -> tools.find { it.id == u.id }?.assignedTo = u.name }
firstOrNull returns the first element matching the condition, or null if there is none. Edit: it seems find is firstOrNull - its implementation just calls firstOrNull.
The ?. safe call operator returns null if the left operand is null, otherwise, it calls the method.
For = and other operators which return Unit (i.e. void, nothing), using the safe call operator simply does nothing if the left operand is null.
If we combine these, it effectively sets the name of the first element which matches this condition.
First, you're missing comma after properties in your data classes, so it should be:
data class Tool(
var id: String = "",
var description: String = "",
var assignedTo: String = ""
)
data class Updated(
var id: String = "",
var assignedTo: String = ""
)
As for second problem, there're probably number of ways to do that, but I've only corrected your idea:
fun updateList(tools: List<Tool>, updateTools: List<Updated>): List<Tool> {
updateTools.forEach{ ut ->
tools.find { it.id == ut.id }?.assignedTo = ut.assignedTo
}
return tools
}
Instead of assigning values to variables, you can name parameter for forEach and use it in rest of the loop.
Is it possible to create a template string as a usual string,
let a = "b:${b}";
and then convert it into a template string,
let b = 10;
console.log(a.template()); // b:10
without eval, new Function and other means of dynamic code generation?
In my project I've created something like this with ES6:
String.prototype.interpolate = function(params) {
const names = Object.keys(params);
const vals = Object.values(params);
return new Function(...names, `return \`${this}\`;`)(...vals);
}
const template = 'Example text: ${text}';
const result = template.interpolate({
text: 'Foo Boo'
});
console.log(result);
As your template string must get reference to the b variable dynamically (in runtime), so the answer is: NO, it's impossible to do it without dynamic code generation.
But, with eval it's pretty simple:
let tpl = eval('`'+a+'`');
No, there is not a way to do this without dynamic code generation.
However, I have created a function which will turn a regular string into a function which can be provided with a map of values, using template strings internally.
Generate Template String Gist
/**
* Produces a function which uses template strings to do simple interpolation from objects.
*
* Usage:
* var makeMeKing = generateTemplateString('${name} is now the king of ${country}!');
*
* console.log(makeMeKing({ name: 'Bryan', country: 'Scotland'}));
* // Logs 'Bryan is now the king of Scotland!'
*/
var generateTemplateString = (function(){
var cache = {};
function generateTemplate(template){
var fn = cache[template];
if (!fn){
// Replace ${expressions} (etc) with ${map.expressions}.
var sanitized = template
.replace(/\$\{([\s]*[^;\s\{]+[\s]*)\}/g, function(_, match){
return `\$\{map.${match.trim()}\}`;
})
// Afterwards, replace anything that's not ${map.expressions}' (etc) with a blank string.
.replace(/(\$\{(?!map\.)[^}]+\})/g, '');
fn = Function('map', `return \`${sanitized}\``);
}
return fn;
}
return generateTemplate;
})();
Usage:
var kingMaker = generateTemplateString('${name} is king!');
console.log(kingMaker({name: 'Bryan'}));
// Logs 'Bryan is king!' to the console.
Hope this helps somebody. If you find a problem with the code, please be so kind as to update the Gist.
What you're asking for here:
//non working code quoted from the question
let b=10;
console.log(a.template());//b:10
is exactly equivalent (in terms of power and, er, safety) to eval: the ability to take a string containing code and execute that code; and also the ability for the executed code to see local variables in the caller's environment.
There is no way in JS for a function to see local variables in its caller, unless that function is eval(). Even Function() can't do it.
When you hear there's something called "template strings" coming to JavaScript, it's natural to assume it's a built-in template library, like Mustache. It isn't. It's mainly just string interpolation and multiline strings for JS. I think this is going to be a common misconception for a while, though. :(
There are many good solutions posted here, but none yet which utilizes the ES6 String.raw method. Here is my contriubution. It has an important limitation in that it will only accept properties from a passed in object, meaning no code execution in the template will work.
function parseStringTemplate(str, obj) {
let parts = str.split(/\$\{(?!\d)[\wæøåÆØÅ]*\}/);
let args = str.match(/[^{\}]+(?=})/g) || [];
let parameters = args.map(argument => obj[argument] || (obj[argument] === undefined ? "" : obj[argument]));
return String.raw({ raw: parts }, ...parameters);
}
let template = "Hello, ${name}! Are you ${age} years old?";
let values = { name: "John Doe", age: 18 };
parseStringTemplate(template, values);
// output: Hello, John Doe! Are you 18 years old?
Split string into non-argument textual parts. See regex.
parts: ["Hello, ", "! Are you ", " years old?"]
Split string into property names. Empty array if match fails.
args: ["name", "age"]
Map parameters from obj by property name. Solution is limited by shallow one level mapping. Undefined values are substituted with an empty string, but other falsy values are accepted.
parameters: ["John Doe", 18]
Utilize String.raw(...) and return result.
TLDR:
https://jsfiddle.net/bj89zntu/1/
Everyone seems to be worried about accessing variables. Why not just pass them? I'm sure it won't be too hard to get the variable context in the caller and pass it down. Use
ninjagecko's answer to get the props from obj.
function renderString(str,obj){
return str.replace(/\$\{(.+?)\}/g,(match,p1)=>{return index(obj,p1)})
}
Here is the full code:
function index(obj,is,value) {
if (typeof is == 'string')
is=is.split('.');
if (is.length==1 && value!==undefined)
return obj[is[0]] = value;
else if (is.length==0)
return obj;
else
return index(obj[is[0]],is.slice(1), value);
}
function renderString(str,obj){
return str.replace(/\$\{.+?\}/g,(match)=>{return index(obj,match)})
}
renderString('abc${a}asdas',{a:23,b:44}) //abc23asdas
renderString('abc${a.c}asdas',{a:{c:22,d:55},b:44}) //abc22asdas
The issue here is to have a function that has access to the variables of its caller. This is why we see direct eval being used for template processing. A possible solution would be to generate a function taking formal parameters named by a dictionary's properties, and calling it with the corresponding values in the same order. An alternative way would be to have something simple as this:
var name = "John Smith";
var message = "Hello, my name is ${name}";
console.log(new Function('return `' + message + '`;')());
And for anyone using Babel compiler we need to create closure which remembers the environment in which it was created:
console.log(new Function('name', 'return `' + message + '`;')(name));
I liked s.meijer's answer and wrote my own version based on his:
function parseTemplate(template, map, fallback) {
return template.replace(/\$\{[^}]+\}/g, (match) =>
match
.slice(2, -1)
.trim()
.split(".")
.reduce(
(searchObject, key) => searchObject[key] || fallback || match,
map
)
);
}
Similar to Daniel's answer (and s.meijer's gist) but more readable:
const regex = /\${[^{]+}/g;
export default function interpolate(template, variables, fallback) {
return template.replace(regex, (match) => {
const path = match.slice(2, -1).trim();
return getObjPath(path, variables, fallback);
});
}
//get the specified property or nested property of an object
function getObjPath(path, obj, fallback = '') {
return path.split('.').reduce((res, key) => res[key] || fallback, obj);
}
Note: This slightly improves s.meijer's original, since it won't match things like ${foo{bar} (the regex only allows non-curly brace characters inside ${ and }).
UPDATE: I was asked for an example using this, so here you go:
const replacements = {
name: 'Bob',
age: 37
}
interpolate('My name is ${name}, and I am ${age}.', replacements)
#Mateusz Moska, solution works great, but when i used it in React Native(build mode), it throws an error: Invalid character '`', though it works when i run it in debug mode.
So i wrote down my own solution using regex.
String.prototype.interpolate = function(params) {
let template = this
for (let key in params) {
template = template.replace(new RegExp('\\$\\{' + key + '\\}', 'g'), params[key])
}
return template
}
const template = 'Example text: ${text}',
result = template.interpolate({
text: 'Foo Boo'
})
console.log(result)
Demo: https://es6console.com/j31pqx1p/
NOTE: Since I don't know the root cause of an issue, i raised a ticket in react-native repo, https://github.com/facebook/react-native/issues/14107, so that once they can able to fix/guide me about the same :)
You can use the string prototype, for example
String.prototype.toTemplate=function(){
return eval('`'+this+'`');
}
//...
var a="b:${b}";
var b=10;
console.log(a.toTemplate());//b:10
But the answer of the original question is no way.
I required this method with support for Internet Explorer. It turned out the back ticks aren't supported by even IE11. Also; using eval or it's equivalent Function doesn't feel right.
For the one that notice; I also use backticks, but these ones are removed by compilers like babel. The methods suggested by other ones, depend on them on run-time. As said before; this is an issue in IE11 and lower.
So this is what I came up with:
function get(path, obj, fb = `$\{${path}}`) {
return path.split('.').reduce((res, key) => res[key] || fb, obj);
}
function parseTpl(template, map, fallback) {
return template.replace(/\$\{.+?}/g, (match) => {
const path = match.substr(2, match.length - 3).trim();
return get(path, map, fallback);
});
}
Example output:
const data = { person: { name: 'John', age: 18 } };
parseTpl('Hi ${person.name} (${person.age})', data);
// output: Hi John (18)
parseTpl('Hello ${person.name} from ${person.city}', data);
// output: Hello John from ${person.city}
parseTpl('Hello ${person.name} from ${person.city}', data, '-');
// output: Hello John from -
I currently can't comment on existing answers so I am unable to directly comment on Bryan Raynor's excellent response. Thus, this response is going to update his answer with a slight correction.
In short, his function fails to actually cache the created function, so it will always recreate, regardless of whether it's seen the template before. Here is the corrected code:
/**
* Produces a function which uses template strings to do simple interpolation from objects.
*
* Usage:
* var makeMeKing = generateTemplateString('${name} is now the king of ${country}!');
*
* console.log(makeMeKing({ name: 'Bryan', country: 'Scotland'}));
* // Logs 'Bryan is now the king of Scotland!'
*/
var generateTemplateString = (function(){
var cache = {};
function generateTemplate(template){
var fn = cache[template];
if (!fn){
// Replace ${expressions} (etc) with ${map.expressions}.
var sanitized = template
.replace(/\$\{([\s]*[^;\s\{]+[\s]*)\}/g, function(_, match){
return `\$\{map.${match.trim()}\}`;
})
// Afterwards, replace anything that's not ${map.expressions}' (etc) with a blank string.
.replace(/(\$\{(?!map\.)[^}]+\})/g, '');
fn = cache[template] = Function('map', `return \`${sanitized}\``);
}
return fn;
};
return generateTemplate;
})();
Still dynamic but seems more controlled than just using a naked eval:
const vm = require('vm')
const moment = require('moment')
let template = '### ${context.hours_worked[0].value} \n Hours worked \n #### ${Math.abs(context.hours_worked_avg_diff[0].value)}% ${fns.gt0(context.hours_worked_avg_diff[0].value, "more", "less")} than usual on ${fns.getDOW(new Date())}'
let context = {
hours_worked:[{value:10}],
hours_worked_avg_diff:[{value:10}],
}
function getDOW(now) {
return moment(now).locale('es').format('dddd')
}
function gt0(_in, tVal, fVal) {
return _in >0 ? tVal: fVal
}
function templateIt(context, template) {
const script = new vm.Script('`'+template+'`')
return script.runInNewContext({context, fns:{getDOW, gt0 }})
}
console.log(templateIt(context, template))
https://repl.it/IdVt/3
I made my own solution doing a type with a description as a function
export class Foo {
...
description?: Object;
...
}
let myFoo:Foo = {
...
description: (a,b) => `Welcome ${a}, glad to see you like the ${b} section`.
...
}
and so doing:
let myDescription = myFoo.description('Bar', 'bar');
I came up with this implementation and it works like a charm.
function interpolateTemplate(template: string, args: any): string {
return Object.entries(args).reduce(
(result, [arg, val]) => result.replace(`$\{${arg}}`, `${val}`),
template,
)
}
const template = 'This is an example: ${name}, ${age} ${email}'
console.log(interpolateTemplate(template,{name:'Med', age:'20', email:'example#abc.com'}))
You could raise an error if arg is not found in template
This solution works without ES6:
function render(template, opts) {
return new Function(
'return new Function (' + Object.keys(opts).reduce((args, arg) => args += '\'' + arg + '\',', '') + '\'return `' + template.replace(/(^|[^\\])'/g, '$1\\\'') + '`;\'' +
').apply(null, ' + JSON.stringify(Object.keys(opts).reduce((vals, key) => vals.push(opts[key]) && vals, [])) + ');'
)();
}
render("hello ${ name }", {name:'mo'}); // "hello mo"
Note: the Function constructor is always created in the global scope, which could potentially cause global variables to be overwritten by the template, e.g. render("hello ${ someGlobalVar = 'some new value' }", {name:'mo'});
You should try this tiny JS module, by Andrea Giammarchi, from github :
https://github.com/WebReflection/backtick-template
/*! (C) 2017 Andrea Giammarchi - MIT Style License */
function template(fn, $str, $object) {'use strict';
var
stringify = JSON.stringify,
hasTransformer = typeof fn === 'function',
str = hasTransformer ? $str : fn,
object = hasTransformer ? $object : $str,
i = 0, length = str.length,
strings = i < length ? [] : ['""'],
values = hasTransformer ? [] : strings,
open, close, counter
;
while (i < length) {
open = str.indexOf('${', i);
if (-1 < open) {
strings.push(stringify(str.slice(i, open)));
open += 2;
close = open;
counter = 1;
while (close < length) {
switch (str.charAt(close++)) {
case '}': counter -= 1; break;
case '{': counter += 1; break;
}
if (counter < 1) {
values.push('(' + str.slice(open, close - 1) + ')');
break;
}
}
i = close;
} else {
strings.push(stringify(str.slice(i)));
i = length;
}
}
if (hasTransformer) {
str = 'function' + (Math.random() * 1e5 | 0);
if (strings.length === values.length) strings.push('""');
strings = [
str,
'with(this)return ' + str + '([' + strings + ']' + (
values.length ? (',' + values.join(',')) : ''
) + ')'
];
} else {
strings = ['with(this)return ' + strings.join('+')];
}
return Function.apply(null, strings).apply(
object,
hasTransformer ? [fn] : []
);
}
template.asMethod = function (fn, object) {'use strict';
return typeof fn === 'function' ?
template(fn, this, object) :
template(this, fn);
};
Demo (all the following tests return true):
const info = 'template';
// just string
`some ${info}` === template('some ${info}', {info});
// passing through a transformer
transform `some ${info}` === template(transform, 'some ${info}', {info});
// using it as String method
String.prototype.template = template.asMethod;
`some ${info}` === 'some ${info}'.template({info});
transform `some ${info}` === 'some ${info}'.template(transform, {info});
Faz assim (This way):
let a = 'b:${this.b}'
let b = 10
function template(templateString, templateVars) {
return new Function('return `' + templateString + '`').call(templateVars)
}
result.textContent = template(a, {b})
<b id=result></b>
Since we're reinventing the wheel on something that would be a lovely feature in javascript.
I use eval(), which is not secure, but javascript is not secure. I readily admit that I'm not excellent with javascript, but I had a need, and I needed an answer so I made one.
I chose to stylize my variables with an # rather than an $, particularly because I want to use the multiline feature of literals without evaluating til it's ready. So variable syntax is #{OptionalObject.OptionalObjectN.VARIABLE_NAME}
I am no javascript expert, so I'd gladly take advice on improvement but...
var prsLiteral, prsRegex = /\#\{(.*?)(?!\#\{)\}/g
for(i = 0; i < myResultSet.length; i++) {
prsLiteral = rt.replace(prsRegex,function (match,varname) {
return eval(varname + "[" + i + "]");
// you could instead use return eval(varname) if you're not looping.
})
console.log(prsLiteral);
}
A very simple implementation follows
myResultSet = {totalrecords: 2,
Name: ["Bob", "Stephanie"],
Age: [37,22]};
rt = `My name is #{myResultSet.Name}, and I am #{myResultSet.Age}.`
var prsLiteral, prsRegex = /\#\{(.*?)(?!\#\{)\}/g
for(i = 0; i < myResultSet.totalrecords; i++) {
prsLiteral = rt.replace(prsRegex,function (match,varname) {
return eval(varname + "[" + i + "]");
// you could instead use return eval(varname) if you're not looping.
})
console.log(prsLiteral);
}
In my actual implementation, I choose to use #{{variable}}. One more set of braces. Absurdly unlikely to encounter that unexpectedly. The regex for that would look like /\#\{\{(.*?)(?!\#\{\{)\}\}/g
To make that easier to read
\#\{\{ # opening sequence, #{{ literally.
(.*?) # capturing the variable name
# ^ captures only until it reaches the closing sequence
(?! # negative lookahead, making sure the following
# ^ pattern is not found ahead of the current character
\#\{\{ # same as opening sequence, if you change that, change this
)
\}\} # closing sequence.
If you're not experienced with regex, a pretty safe rule is to escape every non-alphanumeric character, and don't ever needlessly escape letters as many escaped letters have special meaning to virtually all flavors of regex.
You can refer to this solution
const interpolate = (str) =>
new Function(`return \`${new String(str)}\`;`)();
const foo = 'My';
const obj = {
text: 'Hanibal Lector',
firstNum: 1,
secondNum: 2
}
const str = "${foo} name is : ${obj.text}. sum = ${obj.firstNum} + ${obj.secondNum} = ${obj.firstNum + obj.secondNum}";
console.log(interpolate(str));
I realize I am late to the game, but you could:
const a = (b) => `b:${b}`;
let b = 10;
console.log(a(b)); // b:10
I have absolutely no knowledge in Regex whatsoever. Basically what I'm trying to do is have an error class that I can use to call errors (obviously) which looks like this:
package avian.framework.errors
{
public class AvError extends Object
{
// errors
public static const LAYER_WARNING:String = "Warning: {0} is not a valid layer - the default layer _fallback_ has been used as the container for {1}.";
/**
* Constructor
* Places a warning or error into the output console to assist with misuse of the framework
* #param err The error to display
* #param params A list of Objects to use throughout the error message
*/
public function AvError(err:String, ...params)
{
trace(err);
}
}
}
What I want to be able to do is use the LAYER_WARNING like this:
new AvError(AvError.LAYER_WARNING, targetLayer, this);
And have the output be something along the lines of:
Warning: randomLayer is not a valid layer - the default layer _fallback_ has been used as the container for [object AvChild].
The idea is to replace {0} with the first parameter parsed in ...params, {1} with the second, etc.
I've done a bit of research and I think I've worked out that I need to search using this pattern:
var pattern:RegExp = /{\d}/;
You can use StringUtil
var original:String = "Here is my {0} and my {1}!";
var myStr:String = StringUtil.substitute(original, ['first', 'second']);
Using the g flag in RegExp you can create an array containing all of your {x} matches, then loop through this array and replace each of the matches with the appropriate parameter.
Code:
var mystring:String = "{0} went to {1} on {2}";
function replace(str:String, ...params):String
{
var pattern:RegExp = /{\d}/g;
var ar:Array = str.match(pattern);
var i:uint = 0;
for(i; i<ar.length; i++)
{
str = str.split(ar[i]).join(params[i]);
}
return str;
}
trace(replace(mystring, "marty", "work", "friday")); // marty went to work on friday
i'm assuming you want to have several static constants with varying replacement instances ({0}, {1}, {2}, etc.) in each string constant.
something like this should work - sorry, it's untested:
public function AvError(err:String, ...params)
{
var replacementArray:Array = err.match(new RegExp("{\\d}", "g"));
for (var i:int = 0, i < replacementArray.length, i++)
err = err.replace(new RegExp(replacementArray[i], "g"), params[i]);
trace(err);
}
if you do have several static constants with varying replacement instances, you'll want to check for an appropriate matching amount of …params that are passed.