HttpRequest.getString hitting error function even though its succeeding - json

Question

Wondering if anyone here could help?
Using Polymer Dart I've set up a service to load a Json feed using the following code:
Future loadService(){
return HttpRequest.getString(_serviceURL)
.then(buildView)
.catchError(handleError);
}
When this code executed, it does successfully hit my buildView function, but I'm also getting an error printed out from my handle error function:
void handleError(Error error){
print(error);
}
I have 3 items in my json feed:
[
{
"module": "module-1",
"data": {
"title": "Dynamic Title 1",
"text": "This is the dynamic text for content block 1."
}
},
{
"module": "module-2",
"data": {
"title": "Dynamic Title 2",
"text": "This is the dynamic text for content block 2."
}
},
{
"module": "module-3",
"data": {
"title": "Dynamic Title 3",
"text": "This is the dynamic text for content block 3."
}
}
]
The error I'm getting is: "RangeError: 3".
I can't find a lot of information about what could be causing this. It doesn't seem to be hindering my app, but I would like to clear it up if at all possible. If anyone has any suggestions, I'm all ears.
Thanks!
Edit: as per the suggestion by Günter Zöchbauer
Now I understand the .catchError() function catches errors from the .then() function. I thought it was only going to catch errors around the HttpRequest itself failing.
In buildView I was looping through the json object using a for loop like this:
void buildView(String jsonString){
contentBlocks = JSON.decode(jsonString);
DivElement wrapper = $['content-modules-wrapper'];
for(int i=0; i < contentBlocks.length; i++){
Element element = new Element.tag(contentBlocks[i]['module']);
wrapper.children.add(element);
}
}
Which is wrong, because .length takes the JSON string length (300 something characters) which i think is a bit weird since I've converted it to an object.. anyway, i fixed it by changing the function to this:
void buildView(String jsonString){
contentBlocks = JSON.decode(jsonString);
DivElement wrapper = $['content-modules-wrapper'];
contentBlocks.forEach((block){
Element element = new Element.tag(block['module']);
wrapper.children.add(element);
});
}
Is there a way to get the number of items in a json object like I was trying to do or should you always just loop through it using forEach()?

Answer 1

This error is probably from your buildView. The indexes of the result are from 0 to 2 not from 1 to 3.