Trace

Tracing is the process of logging diagnostic information about your application at runtime. This module is useful for debugging, which could provide detailed info about internal workings.

const traceModule = require("tns-core-modules/trace");

import { enable, disable, isEnabled, categories, setCategories, addCategories, write, isCategorySet } from "tns-core-modules/trace";

Custom Trace Writer

The example shows how to create custom writer and to attached it to the tracing categories.

Create custom writer

const array = new ObservableArray();
const TimestampConsoleWriter = (() => {

    function TimestampConsoleWriter() { }
    TimestampConsoleWriter.prototype.write = function (message, category, type) {
      if (!console) {
        return;
      }

      const msgType = types.isUndefined(type) ? traceModule.messageType.log : type;

      switch (msgType) {
        case traceModule.messageType.log:
            array.push({
                "messageType": "log",
                "date": new Date().toISOString(),
                "message": message,
                "category": category
            });
          break;
        case traceModule.messageType.info:
            array.push({
                "messageType": "info",
                "date": new Date().toISOString(),
                "message": message,
                "category": category
            });
          break;
        case traceModule.messageType.warn:
            array.push({
                "messageType": "warning",
                "date": new Date().toISOString(),
                "message": message,
                "category": category
            });
          break;
        case traceModule.messageType.error:
            array.push({
                "messageType": "error",
                "date": new Date().toISOString(),
                "message": message,
                "category": category
            });
          break;
        default:
          break;
      }
    };

    return TimestampConsoleWriter;
  })();

const array = new ObservableArray();
class TimestampConsoleWriter {
    constructor() { }

    public write(message, category, type) {
        if (!console) {
            return;
        }

        const msgType = isUndefined(type) ? messageType.log : type;

        switch (msgType) {
            case messageType.log:
                array.push({
                    "messageType": "log",
                    "date": new Date().toISOString(),
                    "message": message,
                    "category": category
                });
                break;
            case messageType.info:
                array.push({
                    "messageType": "info",
                    "date": new Date().toISOString(),
                    "message": message,
                    "category": category
                });
                break;
            case messageType.warn:
                array.push({
                    "messageType": "warning",
                    "date": new Date().toISOString(),
                    "message": message,
                    "category": category
                });
                break;
            case messageType.error:
                array.push({
                    "messageType": "error",
                    "date": new Date().toISOString(),
                    "message": message,
                    "category": category
                });
                break;
            default:
                break;
        }
    }
}

Adding custom trace writer

traceModule.setCategories(traceModule.categories.Navigation);
traceModule.enable();
traceModule.clearWriters();
traceModule.addWriter(new TimestampConsoleWriter());

setCategories(categories.Navigation);
enable();
clearWriters();
addWriter(new TimestampConsoleWriter());

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Demo Source

Trace Specific Categories

In this example is demonstrated, how to trace a specific set of event categories, how to add new tracing category and to disable the tracing process at all.

Tracing specific categories of events

traceModule.setCategories(traceModule.categories.concat(
    traceModule.categories.Binding,
    traceModule.categories.Layout,
    traceModule.categories.Style,
    traceModule.categories.ViewHierarchy,
    traceModule.categories.VisualTreeEvents
));
traceModule.enable();

setCategories(categories.concat(
    categories.Binding,
    categories.Layout,
    categories.Style,
    categories.ViewHierarchy,
    categories.VisualTreeEvents
));
enable();

Trace add category

traceModule.addCategories(traceModule.categories.Navigation);

addCategories(categories.Navigation);

Check is category setting

if (traceModule.isCategorySet(traceModule.categories.VisualTreeEvents)) {
    dialogs.alert("VisualTreeEvents category has been set")
    .then(() => {
        console.log("Dialog closed!");
    });
} else {
    dialogs.alert("VisualTreeEvents category has not been set")
    .then(() => {
        console.log("Dialog closed!");
    });
}

if (isCategorySet(categories.VisualTreeEvents)) {
    dialogs.alert("VisualTreeEvents category has been set")
        .then(() => {
            console.log("Dialog closed!");
        });
} else {
    dialogs.alert("VisualTreeEvents category has not been set")
        .then(() => {
            console.log("Dialog closed!");
        });
}

Disable tracing

traceModule.disable();

disable();