Traversing through an array of objects - loops

Question

{
"Catalog": {
"shirts": [
{
"id": "93453951-8427394-234723908",
"name": "Demin Shirt",
"price": 100.0,
"category": "Random Category",
"available": true,
},
{
"id": "93453951-8427394-40325978",
"name": "Random Shirt",
"price": 500.0,
"category": "Random Category",
"available": true,
}
],
"Jeans": [
{
"id": "4802345-348579-5983452-23423",
"name": "Bare Denim Jeans",
"price": 2000.0,
"category": "Some Category",
"available": true,
},
{
"id": "143682137-3481293-239842",
"name": "Levis jeans",
"price": 1000.0,
"category": "Some Category",
"available": true,
}
]
}
}
How do I traverse this array of objects such that I am able to display all the different types of shirt under the category shirt and all the jeans under the heading jeans.
Something like this:
Shirts
Denim Shirt.
Random Shirt
Jeans
Bare Denim Jeans
Levis jeans

Answer 1

Generic Solution
This is an object, not a list, so you can't just plug it into a loop. If you want to loop through all the values and sub-values, you will have to do it recursively.
void recurseObject(dynamic value) {
if (value is List) {
// value is a list, iterate over its children
for (var child in value) {
recurseObject(object);
}
} else if (value is Map) {
// value is an object, iterate over its keys and recurse the corresponding values
for (var key in object.keys) {
print(key);
recurseObject(object[key]);
}
} else {
// value is a primitive, so just print it
print(value);
}
}
Specific to your Object
If your object has a set structure, then you can just grab all the bits you want and set up some nested loops.
final catalog = rootObj['Catalog'] as Map<String, Dynamic>;
for (var category in catalog.keys) {
final categoryList = catalog[category] as List<dynamic>;
print(category);
for (var value in categoryList) {
final name = value['name'];
print(name);
}
}

Answer 2

What you have there is pure JSON. You need to first convert it into a Dart object.
There are a few ways to do the conversion. I've found the easiest way is to use an online converter such as this website: https://app.quicktype.io/
After you convert your JSON to an object, you could traverse it like this:
printCatalog() {
var catalog =
Catalog.fromRawJson("Here's where you need to pass in your JSON");
print("Shirts: ");
catalog.shirts.forEach((shirt) {
print(shirt.name);
});
print("Jeans: ");
catalog.jeans.forEach((jean) {
print(jean.name);
});
}

Answer 3

Just use dart:convert library, and json.decode. Then access whatever you want in your json.
I fixed your JSON as it wasn't set up right, here is the complete solution.
import 'dart:convert';
void main() {
var jsonstring = '''{
"Catalog": {
"shirts": [{
"id": "93453951-8427394-234723908",
"name": "Demin Shirt",
"price": 100.0,
"category": "Random Category",
"available": "true"
},
{
"id": "93453951-8427394-40325978",
"name": "Random Shirt",
"price": 500.0,
"category": "Random Category",
"available": true
}
],
"Jeans": [{
"id": "4802345-348579-5983452-23423",
"name": "Bare Denim Jeans",
"price": 2000.0,
"category": "Some Category",
"available": true
},
{
"id": "143682137-3481293-239842",
"name": "Levis jeans",
"price": 1000.0,
"category": "Some Category",
"available": true
}
]
}
}''';
Map<String, dynamic> data = json.decode(jsonstring);
print("--COOL SHIRTS--");
for (var shirt in data["Catalog"]["shirts"]) {
print(shirt["name"]);
}
print("\n--COOL JEANS--");
for (var jeans in data["Catalog"]["Jeans"]) {
print(jeans["name"]);
}
}
Output:
--COOL SHIRTS--
Demin Shirt
Random Shirt
--COOL JEANS--
Bare Denim Jeans
Levis jeans