Related
How can I make this code SWIFT accepting? I've got two arrays of type ANY one array's value should act as the key, the other one as the appropriate value:
let it_tt_ar = db.pair(keys: "int_test", values: "text_test");
func _pair<K : Hashable, V>(keys: [K], values: [V]) -> Dictionary<K,V> {
var result = Dictionary<K, V>();
for i in 0...(keys.count - 1) {
result[keys[i]] = values[i];
}
return result;
}
func pair (keys: String?, values: String?) -> Dictionary<Int32,Any> {
if let _keys = keys, let _values = values {
let result = _pair(keys: hashtable[_keys] as! [Int32], values: hashtable[_values]!);
return result;
} else {
return [:];
}
}
I can't get it working if the type of the key is unknown. I want to write it like this:
let it_tt_ar = db.pair<Int32,String>(keys: "int_test", values: "text_test");
or
let it_tt_ar = db.pair(keys: "int_test", values: "text_test", kt:(Int32.self,String.self));
... in the last case by catching kt: in the function
But there's seems no chance to win against SWIFT:
cannot specify generic functions
or
Int32 cannot fulfill the hashable protocol
It's terrible! You want to write application logic but 80% of the development time is wasted by got to have fulfill such rules!
It looks like you're trying to turn a pair of arrays into a dictionary, regardless of the type of the array (provided, of course, that the type of the key array element is hashable). Here is one way:
let k : [Int] = [1,2,3]
let v : [String] = ["one", "two", "three"]
func pair<Key, Value>(keyArray keys:[Key], valueArray values:[Value]) -> Dictionary<Key,Value> where Key:Hashable {
zip(keys,values).reduce(into: Dictionary<Key,Value>()) {
(dict, tuple) in dict[tuple.0] = tuple.1
}
}
let result = pair(keyArray: k, valueArray: v)
print(result) // [1: "one", 2: "two", 3: "three"], in some order
Found a solution that works for me:
var db = try DataBaseSqlite(dbfile: "test.db");
try db.select(sql: "int_test, real_test, text_test from stest");
var it = db.valueByKey(key: "int_test");
var rt = db.valueByKey(key: "real_test");
var tt = db.valueByKey(key: "text_test");
let it_tt_ar = db.pair(keys: "int_test", values: "text_test", kt: Int32.self);
let tt_it_ar = db.pair(keys: "text_test", values: "int_test", kt: String.self);
try db.close();
func _pair<K : Hashable, V>(keys: [K], values: [V]) -> Dictionary<K,V> {
var result = Dictionary<K, V>();
for i in 0...(keys.count - 1) {
result[keys[i]] = values[i];
}
return result;
}
func pair<T>(keys: String?, values: String?, kt: T.Type) -> Dictionary<T,Any> {
if let _keys = keys, let _values = values {
let result = _pair(keys: hashtable[_keys] as! [T], values: hashtable[_values]!);
return result;
} else {
return [:];
}
}
Due to lack of supporting a real hashtable in Swift (like c# does), my hashtable is just an Dictionary of <String,Array> which is automatically built up by the select method.
So from an application point of view I can write a more efficient and generic code to query sqlite databases.
dbValueByKey() returns a typed (requested) Array of the column values and pair() returns just a combination of two columns.
Why does the following work?
<something>.stop().animate(
{ 'top' : 10 }, 10
);
Whereas this doesn't work:
var thetop = 'top';
<something>.stop().animate(
{ thetop : 10 }, 10
);
To make it even clearer: At the moment I'm not able to pass a CSS property to the animate function as a variable.
{ thetop : 10 } is a valid object literal. The code will create an object with a property named thetop that has a value of 10. Both the following are the same:
obj = { thetop : 10 };
obj = { "thetop" : 10 };
In ES5 and earlier, you cannot use a variable as a property name inside an object literal. Your only option is to do the following:
var thetop = "top";
// create the object literal
var aniArgs = {};
// Assign the variable property name with a value of 10
aniArgs[thetop] = 10;
// Pass the resulting object to the animate method
<something>.stop().animate(
aniArgs, 10
);
ES6 defines ComputedPropertyName as part of the grammar for object literals, which allows you to write the code like this:
var thetop = "top",
obj = { [thetop]: 10 };
console.log(obj.top); // -> 10
You can use this new syntax in the latest versions of each mainstream browser.
With ECMAScript 2015 you are now able to do it directly in object declaration with the brackets notation:
var obj = {
[key]: value
}
Where key can be any sort of expression (e.g. a variable) returning a value.
So here your code would look like:
<something>.stop().animate({
[thetop]: 10
}, 10)
Where thetop will be evaluated before being used as key.
ES5 quote that says it should not work
Note: rules have changed for ES6: https://stackoverflow.com/a/2274327/895245
Spec: http://www.ecma-international.org/ecma-262/5.1/#sec-11.1.5
PropertyName :
IdentifierName
StringLiteral
NumericLiteral
[...]
The production PropertyName : IdentifierName is evaluated as follows:
Return the String value containing the same sequence of characters as the IdentifierName.
The production PropertyName : StringLiteral is evaluated as follows:
Return the SV [String value] of the StringLiteral.
The production PropertyName : NumericLiteral is evaluated as follows:
Let nbr be the result of forming the value of the NumericLiteral.
Return ToString(nbr).
This means that:
{ theTop : 10 } is the exact same as { 'theTop' : 10 }
The PropertyName theTop is an IdentifierName, so it gets converted to the 'theTop' string value, which is the string value of 'theTop'.
It is not possible to write object initializers (literals) with variable keys.
The only three options are IdentifierName (expands to string literal), StringLiteral, and NumericLiteral (also expands to a string).
ES6 / 2020
If you're trying to push data to an object using "key:value" from any other source, you can use something like this:
let obj = {}
let key = "foo"
let value = "bar"
obj[`${key}`] = value
// A `console.log(obj)` would return:
// {foo: "bar}
// A `typeof obj` would return:
// "object"
Hope this helps someone :)
I have used the following to add a property with a "dynamic" name to an object:
var key = 'top';
$('#myElement').animate(
(function(o) { o[key]=10; return o;})({left: 20, width: 100}),
10
);
key is the name of the new property.
The object of properties passed to animate will be {left: 20, width: 100, top: 10}
This is just using the required [] notation as recommended by the other answers, but with fewer lines of code!
Adding square bracket around the variable works good for me. Try this
var thetop = 'top';
<something>.stop().animate(
{ [thetop] : 10 }, 10
);
You can also try like this:
const arr = [{
"description": "THURSDAY",
"count": "1",
"date": "2019-12-05"
},
{
"description": "WEDNESDAY",
"count": "0",
"date": "2019-12-04"
}]
const res = arr.map(value => {
return { [value.description]: { count: value.count, date: value.date } }
})
console.log(res);
I couldn't find a simple example about the differences between ES6 and ES5, so I made one. Both code samples create exactly the same object. But the ES5 example also works in older browsers (like IE11), wheres the ES6 example doesn't.
ES6
var matrix = {};
var a = 'one';
var b = 'two';
var c = 'three';
var d = 'four';
matrix[a] = {[b]: {[c]: d}};
ES5
var matrix = {};
var a = 'one';
var b = 'two';
var c = 'three';
var d = 'four';
function addObj(obj, key, value) {
obj[key] = value;
return obj;
}
matrix[a] = addObj({}, b, addObj({}, c, d));
Update: As a commenter pointed out, any version of JavaScript that supports arrow functions will also support ({[myKey]:myValue}), so this answer has no actual use-case (and, in fact, it might break in some bizarre corner-cases).
Don't use the below-listed method.
I can't believe this hasn't been posted yet: just use arrow functions with anonymous evaluation!
Completely non-invasive, doesn't mess with the namespace, and it takes just one line:
myNewObj = ((k,v)=>{o={};o[k]=v;return o;})(myKey,myValue);
demo:
var myKey="valueof_myKey";
var myValue="valueof_myValue";
var myNewObj = ((k,v)=>{o={};o[k]=v;return o;})(myKey,myValue);
console.log(myNewObj);
useful in environments that don't support the new {[myKey]: myValue} syntax yet, such as—apparently; I just verified it on my Web Developer Console—Firefox 72.0.1, released 2020-01-08. I stand corrected; just wrap the thing in parenthesis and it works.
(I'm sure you could potentially make some more powerful/extensible solutions or whatever involving clever use of reduce, but at that point you'd probably be better served by just breaking out the Object-creation into its own function instead of compulsively jamming it all inline)
not that it matters since OP asked this ten years ago, but for completeness' sake and to demonstrate how it is exactly the answer to the question as stated, I'll show this in the original context:
var thetop = 'top';
<something>.stop().animate(
((k,v)=>{o={};o[k]=v;return o;})(thetop,10), 10
);
Given code:
var thetop = 'top';
<something>.stop().animate(
{ thetop : 10 }, 10
);
Translation:
var thetop = 'top';
var config = { thetop : 10 }; // config.thetop = 10
<something>.stop().animate(config, 10);
As you can see, the { thetop : 10 } declaration doesn't make use of the variable thetop. Instead it creates an object with a key named thetop. If you want the key to be the value of the variable thetop, then you will have to use square brackets around thetop:
var thetop = 'top';
var config = { [thetop] : 10 }; // config.top = 10
<something>.stop().animate(config, 10);
The square bracket syntax has been introduced with ES6. In earlier versions of JavaScript, you would have to do the following:
var thetop = 'top';
var config = (
obj = {},
obj['' + thetop] = 10,
obj
); // config.top = 10
<something>.stop().animate(config, 10);
2020 update/example...
A more complex example, using brackets and literals...something you may have to do for example with vue/axios. Wrap the literal in the brackets, so
[ ` ... ` ]
{
[`filter[${query.key}]`]: query.value, // 'filter[foo]' : 'bar'
}
ES5 implementation to assign keys is below:
var obj = Object.create(null),
objArgs = (
(objArgs = {}),
(objArgs.someKey = {
value: 'someValue'
}), objArgs);
Object.defineProperties(obj, objArgs);
I've attached a snippet I used to convert to bare object.
var obj = {
'key1': 'value1',
'key2': 'value2',
'key3': [
'value3',
'value4',
],
'key4': {
'key5': 'value5'
}
}
var bareObj = function(obj) {
var objArgs,
bareObj = Object.create(null);
Object.entries(obj).forEach(function([key, value]) {
var objArgs = (
(objArgs = {}),
(objArgs[key] = {
value: value
}), objArgs);
Object.defineProperties(bareObj, objArgs);
});
return {
input: obj,
output: bareObj
};
}(obj);
if (!Object.entries) {
Object.entries = function(obj){
var arr = [];
Object.keys(obj).forEach(function(key){
arr.push([key, obj[key]]);
});
return arr;
}
}
console(bareObj);
If you want object key to be same as variable name, there's a short hand in ES 2015.
New notations in ECMAScript 2015
var thetop = 10;
var obj = { thetop };
console.log(obj.thetop); // print 10
You can do it this way:
var thetop = 'top';
<something>.stop().animate(
new function() {this[thetop] = 10;}, 10
);
This way also you can achieve desired output
var jsonobj={};
var count=0;
$(document).on('click','#btnadd', function() {
jsonobj[count]=new Array({ "1" : $("#txtone").val()},{ "2" : $("#txttwo").val()});
count++;
console.clear();
console.log(jsonobj);
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<span>value 1</span><input id="txtone" type="text"/>
<span>value 2</span><input id="txttwo" type="text"/>
<button id="btnadd">Add</button>
You could do the following for ES5:
var theTop = 'top'
<something>.stop().animate(
JSON.parse('{"' + theTop + '":' + JSON.stringify(10) + '}'), 10
)
Or extract to a function:
function newObj (key, value) {
return JSON.parse('{"' + key + '":' + JSON.stringify(value) + '}')
}
var theTop = 'top'
<something>.stop().animate(
newObj(theTop, 10), 10
)
Why does the following work?
<something>.stop().animate(
{ 'top' : 10 }, 10
);
Whereas this doesn't work:
var thetop = 'top';
<something>.stop().animate(
{ thetop : 10 }, 10
);
To make it even clearer: At the moment I'm not able to pass a CSS property to the animate function as a variable.
{ thetop : 10 } is a valid object literal. The code will create an object with a property named thetop that has a value of 10. Both the following are the same:
obj = { thetop : 10 };
obj = { "thetop" : 10 };
In ES5 and earlier, you cannot use a variable as a property name inside an object literal. Your only option is to do the following:
var thetop = "top";
// create the object literal
var aniArgs = {};
// Assign the variable property name with a value of 10
aniArgs[thetop] = 10;
// Pass the resulting object to the animate method
<something>.stop().animate(
aniArgs, 10
);
ES6 defines ComputedPropertyName as part of the grammar for object literals, which allows you to write the code like this:
var thetop = "top",
obj = { [thetop]: 10 };
console.log(obj.top); // -> 10
You can use this new syntax in the latest versions of each mainstream browser.
With ECMAScript 2015 you are now able to do it directly in object declaration with the brackets notation:
var obj = {
[key]: value
}
Where key can be any sort of expression (e.g. a variable) returning a value.
So here your code would look like:
<something>.stop().animate({
[thetop]: 10
}, 10)
Where thetop will be evaluated before being used as key.
ES5 quote that says it should not work
Note: rules have changed for ES6: https://stackoverflow.com/a/2274327/895245
Spec: http://www.ecma-international.org/ecma-262/5.1/#sec-11.1.5
PropertyName :
IdentifierName
StringLiteral
NumericLiteral
[...]
The production PropertyName : IdentifierName is evaluated as follows:
Return the String value containing the same sequence of characters as the IdentifierName.
The production PropertyName : StringLiteral is evaluated as follows:
Return the SV [String value] of the StringLiteral.
The production PropertyName : NumericLiteral is evaluated as follows:
Let nbr be the result of forming the value of the NumericLiteral.
Return ToString(nbr).
This means that:
{ theTop : 10 } is the exact same as { 'theTop' : 10 }
The PropertyName theTop is an IdentifierName, so it gets converted to the 'theTop' string value, which is the string value of 'theTop'.
It is not possible to write object initializers (literals) with variable keys.
The only three options are IdentifierName (expands to string literal), StringLiteral, and NumericLiteral (also expands to a string).
ES6 / 2020
If you're trying to push data to an object using "key:value" from any other source, you can use something like this:
let obj = {}
let key = "foo"
let value = "bar"
obj[`${key}`] = value
// A `console.log(obj)` would return:
// {foo: "bar}
// A `typeof obj` would return:
// "object"
Hope this helps someone :)
I have used the following to add a property with a "dynamic" name to an object:
var key = 'top';
$('#myElement').animate(
(function(o) { o[key]=10; return o;})({left: 20, width: 100}),
10
);
key is the name of the new property.
The object of properties passed to animate will be {left: 20, width: 100, top: 10}
This is just using the required [] notation as recommended by the other answers, but with fewer lines of code!
Adding square bracket around the variable works good for me. Try this
var thetop = 'top';
<something>.stop().animate(
{ [thetop] : 10 }, 10
);
You can also try like this:
const arr = [{
"description": "THURSDAY",
"count": "1",
"date": "2019-12-05"
},
{
"description": "WEDNESDAY",
"count": "0",
"date": "2019-12-04"
}]
const res = arr.map(value => {
return { [value.description]: { count: value.count, date: value.date } }
})
console.log(res);
I couldn't find a simple example about the differences between ES6 and ES5, so I made one. Both code samples create exactly the same object. But the ES5 example also works in older browsers (like IE11), wheres the ES6 example doesn't.
ES6
var matrix = {};
var a = 'one';
var b = 'two';
var c = 'three';
var d = 'four';
matrix[a] = {[b]: {[c]: d}};
ES5
var matrix = {};
var a = 'one';
var b = 'two';
var c = 'three';
var d = 'four';
function addObj(obj, key, value) {
obj[key] = value;
return obj;
}
matrix[a] = addObj({}, b, addObj({}, c, d));
Update: As a commenter pointed out, any version of JavaScript that supports arrow functions will also support ({[myKey]:myValue}), so this answer has no actual use-case (and, in fact, it might break in some bizarre corner-cases).
Don't use the below-listed method.
I can't believe this hasn't been posted yet: just use arrow functions with anonymous evaluation!
Completely non-invasive, doesn't mess with the namespace, and it takes just one line:
myNewObj = ((k,v)=>{o={};o[k]=v;return o;})(myKey,myValue);
demo:
var myKey="valueof_myKey";
var myValue="valueof_myValue";
var myNewObj = ((k,v)=>{o={};o[k]=v;return o;})(myKey,myValue);
console.log(myNewObj);
useful in environments that don't support the new {[myKey]: myValue} syntax yet, such as—apparently; I just verified it on my Web Developer Console—Firefox 72.0.1, released 2020-01-08. I stand corrected; just wrap the thing in parenthesis and it works.
(I'm sure you could potentially make some more powerful/extensible solutions or whatever involving clever use of reduce, but at that point you'd probably be better served by just breaking out the Object-creation into its own function instead of compulsively jamming it all inline)
not that it matters since OP asked this ten years ago, but for completeness' sake and to demonstrate how it is exactly the answer to the question as stated, I'll show this in the original context:
var thetop = 'top';
<something>.stop().animate(
((k,v)=>{o={};o[k]=v;return o;})(thetop,10), 10
);
Given code:
var thetop = 'top';
<something>.stop().animate(
{ thetop : 10 }, 10
);
Translation:
var thetop = 'top';
var config = { thetop : 10 }; // config.thetop = 10
<something>.stop().animate(config, 10);
As you can see, the { thetop : 10 } declaration doesn't make use of the variable thetop. Instead it creates an object with a key named thetop. If you want the key to be the value of the variable thetop, then you will have to use square brackets around thetop:
var thetop = 'top';
var config = { [thetop] : 10 }; // config.top = 10
<something>.stop().animate(config, 10);
The square bracket syntax has been introduced with ES6. In earlier versions of JavaScript, you would have to do the following:
var thetop = 'top';
var config = (
obj = {},
obj['' + thetop] = 10,
obj
); // config.top = 10
<something>.stop().animate(config, 10);
2020 update/example...
A more complex example, using brackets and literals...something you may have to do for example with vue/axios. Wrap the literal in the brackets, so
[ ` ... ` ]
{
[`filter[${query.key}]`]: query.value, // 'filter[foo]' : 'bar'
}
ES5 implementation to assign keys is below:
var obj = Object.create(null),
objArgs = (
(objArgs = {}),
(objArgs.someKey = {
value: 'someValue'
}), objArgs);
Object.defineProperties(obj, objArgs);
I've attached a snippet I used to convert to bare object.
var obj = {
'key1': 'value1',
'key2': 'value2',
'key3': [
'value3',
'value4',
],
'key4': {
'key5': 'value5'
}
}
var bareObj = function(obj) {
var objArgs,
bareObj = Object.create(null);
Object.entries(obj).forEach(function([key, value]) {
var objArgs = (
(objArgs = {}),
(objArgs[key] = {
value: value
}), objArgs);
Object.defineProperties(bareObj, objArgs);
});
return {
input: obj,
output: bareObj
};
}(obj);
if (!Object.entries) {
Object.entries = function(obj){
var arr = [];
Object.keys(obj).forEach(function(key){
arr.push([key, obj[key]]);
});
return arr;
}
}
console(bareObj);
If you want object key to be same as variable name, there's a short hand in ES 2015.
New notations in ECMAScript 2015
var thetop = 10;
var obj = { thetop };
console.log(obj.thetop); // print 10
You can do it this way:
var thetop = 'top';
<something>.stop().animate(
new function() {this[thetop] = 10;}, 10
);
This way also you can achieve desired output
var jsonobj={};
var count=0;
$(document).on('click','#btnadd', function() {
jsonobj[count]=new Array({ "1" : $("#txtone").val()},{ "2" : $("#txttwo").val()});
count++;
console.clear();
console.log(jsonobj);
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<span>value 1</span><input id="txtone" type="text"/>
<span>value 2</span><input id="txttwo" type="text"/>
<button id="btnadd">Add</button>
You could do the following for ES5:
var theTop = 'top'
<something>.stop().animate(
JSON.parse('{"' + theTop + '":' + JSON.stringify(10) + '}'), 10
)
Or extract to a function:
function newObj (key, value) {
return JSON.parse('{"' + key + '":' + JSON.stringify(value) + '}')
}
var theTop = 'top'
<something>.stop().animate(
newObj(theTop, 10), 10
)
I have a variable :
var name = [Nick,John,Peter]
and a function:
func name(){
var personname = []
.......
return personname
}
the result of the function are the names of the people Nick,John,Peter. How can I return the result into the variable.I mean I do not want to write the names manually I want to populate them from the function, because the function display all of the names. I am beginner and I will be glad if you show me the right syntaxis.
var name = [????] = [personname()] or how????
You should use -> to return something from a function. Here is an example:
static let people = ["Nick", "John", "Peter"]
func getPerson(index: Int) -> String
{
return self.people[index] //index is number of a person, 0 will be the first one, 1 is second, etc.
}
func showTeam()
{
// some code
print("This is a first boy: \(self.getPerson[0])")
// some code
}
I am using Select2 to help select more than one option in a list. The problem is, is that I have the same code repeated when I want to have the same function for a portion of the form.
I would like to know a way to DRY up my code. Many thanks.
$(document).ready ->
$(".universities-select2").each (i, e) ->
select = $(e)
options = {}
if select.hasClass("ajax")
options.ajax =
url: select.data("source")
dataType: "json"
data: (term, page) ->
q: term
page: page
per: 10
results: (data, page) ->
results: data
options.dropdownCssClass = "bigdrop"
options.multiple = true
options.width = "200px"
options.initSelection = (element, callback) ->
id = undefined
id = $(element).val()
if id isnt null
$.ajax(
url: '/universities/multiple'
dataType: "json"
data:
id: id
).done (data) ->
results = undefined
results = []
callback data
return
select.select2 options
return
return
$(document).ready ->
$(".skills-select2").each (i, e) ->
select = $(e)
options = {}
if select.hasClass("ajax")
options.ajax =
url: select.data("source")
dataType: "json"
data: (term, page) ->
q: term
page: page
per: 10
results: (data, page) ->
results: datea
options.dropdownCssClass = "bigdrop"
options.multiple = true
options.width = "200px"
options.initSelection = (element, callback) ->
id = undefined
id = $(element).val()
if id isnt null
$.ajax(
url: '/skills/multiple'
dataType: "json"
data:
id: id
).done (data) ->
results = undefined
results = []
callback data
return
select.select2 options
return
return
You can just make the class name a variable and name your function
So:
setupSelect = (target) ->
$(target).each (i, e) ->
select = $(e)
#etc
$ ->
setupSelect('.universities-select2')
setupSelect('.skills-select2')
Of course you can also select more than one class with a jquery selector, so if its just these 2 you can do this
$('.universities-select2, .skills-select2')