Related
I am trying to find the easiest way to sort an array without using sort() function. I tried searching but i could not find any questions that were on SWIFT. I found several questions about php and javascript and so far nothing on swift.
var arr = [7,6456,2135,164,1345,4,8,5,87456,123,2,87,724,6523,1]
var arrSorted = arr
var index = arr.count
repeat {
var previousSwapIndex = 0
for i in 1..<index {
if (arrSorted[i - 1] as! Int) > (arrSorted[i] as! Int) {
let prevVal = arrSorted[i - 1]
let currentVal = arrSorted[i]
arrSorted[i] = prevVal
arrSorted[i - 1] = currentVal
previousSwapIndex = i
}
}
index = previousSwapIndex
} while (index != 0)
print(arrSorted as Array)
This method works but i am looking for something that is better than this and easier than this.
(Edit[Clarification] :- better = faster / quicker ,as this iterates 120 times before the array is sorted)
Could someone help me out?
Here's a generic implementation of insertion sort in Swift. It takes an inout array, but you should be able to modify it to return an array if that's what you want.
func sort<T: Comparable>(_ array: inout [T]) {
var i = 1
while i < array.count {
var x = array[i]
var j = i - 1
while j >= 0 && array[j] > x {
array[j+1] = array[j]
j -= 1
}
array[j+1] = x
i += 1
}
}
To use it:
var intArr = [1, 7, 3, 6, 4]
sort(&intArr)
print(intArr) // [1, 3, 4, 6, 7]
var stringArr = ["hello", "goodbye", "a", "string", "z", "another string"]
sort(&stringArr)
print(stringArr) // ["a", "another string", "goodbye", "hello", "string", "z"]
It will work on any type that conforms to Comparable.
You can find about all the different methods of sorting from this git.
https://github.com/raywenderlich/swift-algorithm-club
I checked a few and none of them are using any .sort() functions. Pick whichever feels easier for you.
var unsortedStringArray = ["B", "C", "Z", "A", "H"]
var unsortedIntArray = [7,8,3,4,5,9,1,2,6]
func sortFunction<T:Comparable>(array: [T]) -> [T]{
var unsortedArray = array
for i in 0..<unsortedArray.count {
for j in 0..<unsortedArray.count{
var temp: T
if unsortedArray[i] < unsortedArray[j] {
temp = unsortedArray[i]
unsortedArray[i] = unsortedArray[j]
unsortedArray[j] = temp
}
}
}
return unsortedArray
}
let resultStringArray = sortFunction(array: unsortedStringArray)
let resultIntArray = sortFunction(array: unsortedIntArray)
print(resultStringArray) //["A", "B", "C", "H", "Z"]
print(resultIntArray) // [1, 2, 3, 4, 5, 6, 7, 8, 9]
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 an array of dictionaries that appears as below and I want to sort and store it such that the objects are sorted based on the 'value' of the 'Like' key ? How do I do this in Swift ? Thanks.
{
Dislike = 0;
Like = 5;
userName = T; }
{
Dislike = 0;
Like = 0;
userName = S; }
{
Dislike = 0;
Like = 10;
userName = N; }
I suppose that's an array of dictionaries?
If it is the case, you can sort them as follows
//AnyObject in case your number is an NSNumber
var array: [[String:AnyObject?]] = yourArray
array.sort{ $0["Like"]!! > $1["Like"]!! }
basically it mutates the array and sort based on the "Like" key.
This data structure looks really weird you know. I think it is a [[String: Any]]. It should be declared like this:
let data: [[String: Any]] = [
[
"Dislike": 0,
"Like": 5,
"username": "T"],
[
"Dislike": 0,
"Like": 0,
"username": "S"],
[
"Dislike": 0,
"Like": 10,
"username": "N"],
]
To sort it, simply use the sort function. In the closure, you should return whether the first parameter should be ordered before the second parameter. In this case, you would like to only compare the values corresponding to the key "Like". The closure body would look something like this: (pseudocode)
firstParameter["Like"] < secondParameter["Like"]
as I said, that is pseudocode. The real code is a little more complicated:
data.sort { ($0["Like"]! as! Int) < ($1["Like"] as! Int) }
Sweeper and Edder are right, it looks like an array of structs. You can also omit the semicolon.
struct s {
var Dislike: Int = 0
var Like: Int = 0
var userName: String = ""
}
var myArray = [s]()
var i = s()
i.Dislike = 0
i.Like = 5
i.userName = "T"
myArray.append(i)
i.Dislike = 0
i.Like = 0
i.userName = "S"
myArray.append(i)
i.Dislike = 0
i.Like = 10
i.userName = "N"
myArray.append(i)
myArray.sort{$0.Like < $1.Like}
I am using the AmCharts. I need to display value in the balloon text , that value is not a value field.
For example : X axis Value 0 , Y axis 1, (0,1) is 2 ; (1,2) is 5.
I need to display the Difference between the values (0,1) and (1,2) - that means "3" as Balloon in the point (1,2). Any ideas ?
Yes, the chart on your screenshot is possible to implement.
At first, add additional fields to your chart data, for example, labelGraph1, labelGraph2. Then you can use the labelText property of the AmCharts.AmGraph object.
var chartData = [{
title: "Apples",
value1: 24,
value2: 28,
labelGraph1: null,
labelGraph2: null
}, {
title: "Bananas",
value1: 27,
value2: 31,
labelGraph1: null,
labelGraph2: null
}, {
title: "Cherries",
value1: 27,
value2: 39,
labelGraph1: null,
labelGraph2: null
}];
for(var i = 0; i < chartData.length; i++) {
chartData[i].labelGraph1 = chartData[i].value1;
chartData[i].labelGraph2 = chartData[i].value2 - chartData[i].value1;
}
var chart;
AmCharts.ready(function () {
// SERIAL CHART
chart = new AmCharts.AmSerialChart();
chart.dataProvider = chartData;
chart.categoryField = "title";
// GRAPHS
var graph1 = new AmCharts.AmGraph();
graph1.valueField = "value1";
graph1.type = "line";
graph1.fillAlphas = 0.6;
graph1.labelText = "[[labelGraph1]]";
chart.addGraph(graph1);
var graph2 = new AmCharts.AmGraph();
graph2.valueField = "value2";
graph2.type = "line";
graph2.fillAlphas = 0.6;
graph2.labelText = "[[labelGraph2]]";
chart.addGraph(graph2);
// WRITE
chart.write("chartdiv")
});
The only one difficulty is to calculate values of the displayed fields.
I did it so, and you should change that function according to your data:
for(var i = 0; i < chartData.length; i++) {
chartData[i].labelGraph1 = chartData[i].value1;
chartData[i].labelGraph2 = chartData[i].value2 - chartData[i].value1;
}