Reading App Logs

Pro plan or higher required Build errors show problems at compile time. But what about issues that happen while your app is running? That’s where app logs come in.

What Are App Logs?

Logs are messages your app produces while running. They show:

What code is executing
Values of variables
Errors that occur at runtime
User actions and their effects

Accessing Logs in Nativeline

Open the Code Editor

Click the Code Editor tab in the Nativeline interface.

Switch to Logs View

Find and click the Logs tab or section within the Code Editor.

Run Your App

Build and run your app. Logs appear in real-time.

Watch the Output

As you interact with your app, logs show what’s happening.

Understanding Log Output

Basic Log Structure

2024-01-15 10:30:45.123 MyApp[12345:67890] Save button tapped
2024-01-15 10:30:45.456 MyApp[12345:67890] Saving data: User(name: "John")
2024-01-15 10:30:45.789 MyApp[12345:67890] Save completed successfully

Each line shows:

Timestamp: When it happened
App name: Which app
Message: The actual log content

Log Types

Type	Meaning
Info logs	Normal operation, status updates
Warning logs	Something unusual, but not critical
Error logs	Something went wrong
Debug logs	Developer debugging info

Adding Logs to Your App

Ask the AI to add logging:

For Debugging a Specific Feature

Add print statements to the saveData function to show:
- When the function starts
- What data is being saved
- Whether the save succeeded or failed

Add logging for all button taps so I can see what users are doing

For API/Network Issues

Add logging to show:
- When API requests start
- What data is being sent
- What response comes back
- Any errors that occur

Common Debugging Scenarios

Debugging “Nothing Happens” Issues

Your button doesn’t seem to work? Add logs:

Add a print statement at the start of the button's action
to confirm it's being triggered

If the log appears: The button works, the issue is in the code after. If no log appears: The button isn’t connected properly.

Debugging Data Issues

Data not showing up?

Add logging to show:
- When data is loaded
- How many items were loaded
- The actual content of the first item

Check the logs to see if data exists and what it contains. Screen not appearing?

Add logging when the navigation to [screen] is triggered
and when [screen] appears

Follow the trail to see where it breaks.

Debugging Crash-Like Behavior

App freezing or behaving strangely?

Add extensive logging throughout [feature] to trace exactly
where the problem occurs

The last log before the freeze indicates where to look.

Reading Swift Error Messages

When Swift errors appear in logs, they often include useful info:

Optional Unwrapping Errors

Fatal error: Unexpectedly found nil while unwrapping an Optional value

Meaning: Your code tried to use a nil value that should have had a value. Fix: Ask the AI to add nil checking for the relevant variable.

Array Index Errors

Fatal error: Index out of range

Meaning: Accessing an array position that doesn’t exist. Fix: Check array bounds before accessing, or verify the data exists.

Type Casting Errors

Could not cast value of type 'X' to 'Y'

Meaning: Tried to convert between incompatible types. Fix: Check the actual type and handle it appropriately.

Effective Logging Strategies

1. Log Entry and Exit

print("▶️ saveProfile started")
// ... code ...
print("✅ saveProfile completed")

This shows whether functions complete or exit early.

2. Log Important Values

print("📊 User data: \(userData)")
print("📊 Items count: \(items.count)")

See what your variables actually contain.

3. Log Decision Points

if isLoggedIn {
    print("🔓 User is logged in, showing profile")
} else {
    print("🔒 User not logged in, showing login")
}

Understand which code paths execute.

4. Use Distinctive Markers

Using emojis or prefixes makes logs easier to scan:

▶️ Start of function
✅ Success
❌ Error
⚠️ Warning
📊 Data values
🔄 State changes

Filtering and Searching Logs

When there’s a lot of output:

Search for Specific Text

Look for your custom log messages or error keywords.

Filter by Feature

If you’re debugging the save feature, search for “save” in logs.

Filter by Error Level

Look for “error”, “failed”, “nil”, or “crash” to find problems.

When to Use Logs vs Build Errors

Situation	Check
App won’t compile	Build errors in chat
App compiles but crashes	Runtime logs
App runs but feature doesn’t work	Runtime logs
UI looks wrong	Visual inspection + logs
Data doesn’t save	Logs showing save operations
API not working	Logs showing requests/responses

Removing Debug Logs

Before publishing your app, clean up debug logs:

Remove all the debug print statements we added for troubleshooting.
Keep only important error logging.

Or for more control:

Replace debug print statements with proper logging that only
shows in debug builds, not in production.

Advanced: Console.app

For even more detailed debugging, you can use macOS’s Console app:

Open Console.app (in Applications → Utilities)
Select your Simulator in the sidebar
Run your app
See comprehensive system logs

This shows logs from iOS itself, not just your app.

Troubleshooting

Logs aren't appearing

Make sure your app is running
Check you’re on the Logs tab
Try adding explicit print statements
Restart the Simulator

Too many logs to read

Add distinctive prefixes to your logs
Search for specific terms
Ask the AI to reduce logging: “Only log errors, not normal operations”

Don't have logs tab

The Logs feature requires Pro plan or higher. Check your subscription in Settings.

Guides

Reading App Logs

Reading App Logs

What Are App Logs?

Accessing Logs in Nativeline

Understanding Log Output

Basic Log Structure

Log Types

Adding Logs to Your App

For Debugging a Specific Feature

For Tracking User Actions

For API/Network Issues

Common Debugging Scenarios

Debugging “Nothing Happens” Issues

Debugging Data Issues

Debugging Navigation Issues

Debugging Crash-Like Behavior

Reading Swift Error Messages

Optional Unwrapping Errors

Array Index Errors

Type Casting Errors

Effective Logging Strategies

1. Log Entry and Exit

2. Log Important Values

3. Log Decision Points

4. Use Distinctive Markers

Filtering and Searching Logs

Search for Specific Text

Filter by Feature

Filter by Error Level

When to Use Logs vs Build Errors

Removing Debug Logs

Advanced: Console.app

Troubleshooting

Next Steps

Debugging Guide

Code Editor

​Reading App Logs

​What Are App Logs?

​Accessing Logs in Nativeline

​Understanding Log Output

​Basic Log Structure

​Log Types

​Adding Logs to Your App

​For Debugging a Specific Feature

​For Tracking User Actions

​For API/Network Issues

​Common Debugging Scenarios

​Debugging “Nothing Happens” Issues

​Debugging Data Issues

​Debugging Navigation Issues

​Debugging Crash-Like Behavior

​Reading Swift Error Messages

​Optional Unwrapping Errors

​Array Index Errors

​Type Casting Errors

​Effective Logging Strategies

​1. Log Entry and Exit

​2. Log Important Values

​3. Log Decision Points

​4. Use Distinctive Markers

​Filtering and Searching Logs

​Search for Specific Text

​Filter by Feature

​Filter by Error Level

​When to Use Logs vs Build Errors

​Removing Debug Logs

​Advanced: Console.app

​Troubleshooting

​Next Steps

Debugging Guide

Code Editor

Reading App Logs

What Are App Logs?

Accessing Logs in Nativeline

Understanding Log Output

Basic Log Structure

Log Types

Adding Logs to Your App

For Debugging a Specific Feature

For Tracking User Actions

For API/Network Issues

Common Debugging Scenarios

Debugging “Nothing Happens” Issues

Debugging Data Issues

Debugging Navigation Issues

Debugging Crash-Like Behavior

Reading Swift Error Messages

Optional Unwrapping Errors

Array Index Errors

Type Casting Errors

Effective Logging Strategies

1. Log Entry and Exit

2. Log Important Values

3. Log Decision Points

4. Use Distinctive Markers

Filtering and Searching Logs

Search for Specific Text

Filter by Feature

Filter by Error Level

When to Use Logs vs Build Errors

Removing Debug Logs

Advanced: Console.app

Troubleshooting

Next Steps