I tried to handle exception like this.
try {
// some functions that likely to throw error
} catch (e) {
print(e);
}
but this print(e) didn't tell me where error come from, it only tell me what error is.
I want to know where error come from and have links that navigate to that line. like this
I also don't want to log on release version, so print is not my anwser.
Can you please give any example on how to do this?
There's a couple of options here depending on whether or not you'll want to be able to control logging output throughout your application or if this is a one-off situation.
Solution 1: make use of asserts
In Dart, assert(...) invocations are only included in debug builds (e.g. processes started via flutter run or dart --enable-asserts foo.dart). You can utilize this fact to conditionally execute code depending on whether or not your program is running in release by doing the following:
assert(() {
print('debug-only logging');
}());
Solution 2: use package:logging
A more general solution is to use package:logging to set up a global Logger instance and then only log through that interface. This package lets you write logs with different verbosities and the level property of Logger can be used to determine which log levels are actually printed. This can be combined with solution #1 to conditionally enable logging throughout the application only while debugging:
void main() {
// Disable logs by default.
myLogger.level = Level.OFF;
assert(() {
// Enable logs in debug mode.
myLogger.level = Level.ALL;
}());
// Your logic here
// ...
}
Related
I just cannot figure out how to show logging messages when running dart files from terminal.
Example example.dart:
import 'dart:developer';
void main() {
print('print');
log('log');
}
Expected output:
print
log
Actual output:
print
I tried calling dart example.dart, dart run --all example.dart, dart run --verbosity=all example.dart, and different values instead of all (info, ...).
But non of these produced any helpful error messages let alone the out print I expect.
APIs from dart:developer (such as log) are intended to interact with debugging tools:
Interact with developer tools such as the debugger and inspector.
It's not explicit from the documentation for log, but I'd expect it to send a log message only to an attached debugger, not to the console.
If you want logging output that is independent of a debugger, use package:logging and add a listener that calls print, as shown by the example.
I have pipeline which will trigger from SCM. I want to capture most of the information about what went wrong if build fails and needed information if build succeed. All the captured info i will be using it in mail body(As detail as possible). I want to know how to capture those info and Do i need to use try catch or is there any other way?
Could anyone help me with the solution please?
I did something similar in the scripted pipeline.
Certainly, you need to use try/catch/finally as the sending email step needs to run no matter build pass or fail; you need to catch the exception so that you can take useful information out of it and then finally run the send email step.
At a high level, it will look like this
try {
// put your stages/logic here
} catch (ex) {
// get exception details ex.message etc
throw ex
} finally {
// put the email step
}
I am aware of two methods of determining whether my app is in running in debug mode:
const bool.fromEnvironment("dart.vm.product") returns true if release.
And this from the Sentry part of the Flutter docs:
bool get isInDebugMode {
// Assume we're in production mode
bool inDebugMode = false;
// Assert expressions are only evaluated during development. They are ignored
// in production. Therefore, this code will only turn `inDebugMode` to true
// in our development environments!
assert(inDebugMode = true);
return inDebugMode;
}
Are those two always equivalent or are there situations where they would give different answers? Which should I use? The first method being compile time seems to favour it.
In general they should be the same, but there can be differences.
const bool.fromEnvironment("dart.vm.product") depends on release build being performed. I haven't checked if profile build returns true or false
assert(inDebugMode = true); depends on asserts being enabled.
asserts are enabled in debug mode by default and disabled in release builds by default but there should be a way to enable/disable asserts independently of release/debug mode, but I haven't found how. Perhaps it's not exposed in Flutter or it is not implemented in Dart yet.
I'd think bool.fromEnvironment() works better with tree-shaking because it can be used to create a const value.
Created a webextension for firefox (currently using Nightly 52), that uses native messaging to launch a java program on Linux (Ubuntu 14, 32x).
The webextension loads, reads the .json file and reads the path which points to a script that starts the java program. The JSON and the path are correct as when I use:
var native = browser.runtime.connectNative("passwordmanager");
console.log("native.name" + native.name); //outputs passwordmanager.
native.onDisconnect.addListener(function(m) { console.log("Disconnected"); });
The above code prints the name of the native port and also prints "Disconnected". So I m guessing the native app is terminating for some reason.
The application is only skeleton right now, that just does sysout and reads sysin and works correctly if Launch it directly through the shell script.
While debugging the webextension, I am not able to step into the call to connectNative, as it just steps-over that call instead of doing step-in. So kind of out of options whats' going wrong.
Please let me know if anyone is able to create a native messaging app based on FF webextension and any pointers on what I might be doing wrong.
Thanks
This solution here shows you how to detect onConnect and onFail. It should help you out to figure out your real problem.
So I don't think you can do proper error handling with connectNative from the JS side alone. You can do somewhat error handling if you get the exe side involved, but you can't get a string for "error reason" when an error occurs. The error is only logged to console.
First make sure to set your deeloper prefs, so messages show in your browser console. You can use this addon - https://addons.mozilla.org/en-US/firefox/addon/devprefs/ - or read that addon description it gives you the MDN page with the prefs to set.
Then this is how you can do some sort of error handling (without error reason) (pseudo-code - i might need a .bind in the callbcks):
function connectNative(aAppName, onConnect, onFail) {
var listener = function(payload) {
if (!connected) {
connected = true;
port.onDisconnect.removeListener(failedConnect);
onConnect();
} else {
// process messages
}
}
var failedConnect = function() {
onFail('failed for unattainable reason - however see browser console as it got logged there');
}
var connected = false;
var port = chrome.runtime.connectNative(aAppName);
port.onMessage.addListener(listener);
port.onDisconnect.addListener(failedConnect);
return port;
}
Now in your exe, as soon as it starts up, make it write to stdout something. That will trigger the onConnect.
I am doing coding from beggining blackberry by Anthony Rizk.
I am stuck with this code as it is showing error again and again...
private void getURL() {
HttpRequestDispatcher dispatcher = new HttpRequestDispatcher(urlField.getText(),
"GET", this);
dispatcher.start();
}
Can anyone explain me why we are passing this as parameter and why actually this code is doing...
"this" refers to the main screen you passed to the class so you can alert the requestFailed string. Check the run method on page 170. You'll see screen.requestFailed("Unexpected...").
As for your error - I suggest adding this line:
System.out.println(" ----------------- HTTPREQUESTDISPATCHER ---------- " + urlField.getText());
right before your dispatcher.start(); line and then compile in debug mode to see what your console says. Just to make sure your URL to request is a valid web URL.
Additionally, make sure your simulator has MDS enabled. You need that to make web calls.
In eclipse it is under Run->run configurations-> simulator tab -> general -> checkbox for Mobile Data System.
I don't know where it is in the RIM package. If you're not using eclipse, you might want to switch over to it. It will highlight errors and try to help you resolve them.