Breakpoints

Breakpoints are special markers that suspend program execution at a specific point. This lets you examine the program state and behavior. Breakpoints can be simple (for example, suspending the program on reaching some line of code) or involve more complex logic (checking against additional conditions, writing log messages, and so on).

Once set, a breakpoint remains in your project until you remove it explicitly, except for temporary breakpoints).

Types of breakpoints

The following types of breakpoints are available in AppCode:

Line breakpoints: suspend the program upon reaching the line of code where the breakpoint was set. This type of breakpoints can be set on any executable line of code.
Exception breakpoints: suspend the program when NSException (for Objective-C) or Error (for Swift) or their subclasses are thrown. They apply globally to the exception condition and do not require a particular source code reference.
Symbolic breakpoints: suspend the program when a specific function or method are executed.

Set breakpoints

Set line breakpoints

Click the gutter at the executable line of code where you want to set the breakpoint. Alternatively, place the caret at the line and press ⌃ F8.

Set exception breakpoints

Click View Breakpoints in the left part of the Debug tool window or press ⌃ ⇧ F8.
In the Breakpoints dialog, press ⌘ N or click , and select Exception Breakpoints or JavaScript Exception Breakpoint.
For Exception Breakpoint, you can specify when you want to suspend the program: when any or an Objective-C only exception is thrown.

Set symbolic breakpoints

Click View Breakpoints in the left part of the Debug tool window or press ⌃ ⇧ F8.
In the Breakpoints dialog, press ⌘ N or click , and select Symbolic Breakpoints.
Specify the symbol name and select whether you want this breakpoint to be hit in all modules, or in a specific module only.

Manage breakpoints

Remove breakpoints

For line breakpoints: click the breakpoint in the gutter.
For all breakpoints: from the main menu, select Run | View Breakpoints ⌃ ⇧ F8, select the breakpoint, and click Remove ⌦.

To avoid accidentally removing a breakpoint and losing its parameters, you can choose to remove breakpoints by dragging them to the editor or clicking the middle mouse button. To do this, go to Preferences | Build, Execution, Deployment | Debugger and select Drag to the editor or click with middle mouse button. Clicking a breakpoint will then enable or disable it.

Mute breakpoints

If you don't need to stop at your breakpoints for some time, you can mute them. This allows you to resume normal program operation without leaving the debugger session. After that, you can unmute breakpoints and continue debugging.

Click the Mute Breakpoints button in the toolbar of the Debug tool window.

Enable/disable breakpoints

When you remove a breakpoint, its internal configuration is lost. To temporarily turn an individual breakpoint off without losing its parameters, you can disable it:

For line breakpoints: right-click it and set the Enabled option as required. You can also toggle them with the middle mouse button if removing breakpoints is not assigned to it.
For all breakpoints: click View Breakpoints ⌃ ⇧ F8 and check/uncheck the breakpoint on the list.

Move/copy breakpoints

To move a breakpoint, drag it to another line.
To copy a breakpoint, hold Ctrl and drag a breakpoint to another line. This creates a breakpoint with the same parameters at the destination.

Configure breakpoints' properties

Depending on the breakpoint type, you can configure additional properties which allow you to tailor its operation for specific needs. The most used options are available via intentions.

To access breakpoint intentions, place the caret at the line with the breakpoint and press ⌥ ⏎. Use this option when you need to quickly configure basic breakpoint properties.
To access the full list of properties, right-click the breakpoint and click More or press ⌃ ⇧ F8. Use this option for a bird's eye view of all breakpoints and full control over their configuration.

Intentions reference

Intention	Description
Remove breakpoint	Removes the breakpoint at the selected line.
Disable breakpoint	Disables the breakpoint at the selected line.
Edit breakpoint	Opens a dialog with the most used breakpoint properties. For more properties, click More or press `⌃ ⇧ F8`.

Breakpoints' properties

Option	Description	Breakpoint type
Enabled	Clear the checkbox to temporarily disable a breakpoint without removing it from the project. Disabled breakpoints will be skipped during the debugging process.	All types
Suspend	Select the checkbox to pause the program execution when a breakpoint is hit. Suspending an application is useful if you need to obtain logging information or calculate an expression at a certain point without interrupting the program. If you need to create a master breakpoint that will trigger dependent breakpoints when hit, choose not to suspend the program at that breakpoint.	All types
Condition	Select to specify a condition for hitting a breakpoint. A condition is any boolean expression that evaluates to `true` or `false`. This expression must be valid at the line where the breakpoint is set, and it is evaluated each time the breakpoint is hit. If the evaluation result is `true`, the selected actions are performed. In this field, you can enter multi-line conditional expressions.	Line Symbolic
Log	Select if you want to log the following events to the console: "Breakpoint hit" message: a log message will be displayed in the console output when the breakpoint is hit. Stack trace: when the breakpoint is hit, its stack trace will be printed to the console. This is useful if you want to check what paths have led to this point without interrupting the program's execution.	All types
Evaluate and log	Select to evaluate an expression when the breakpoint is hit, and show the result in the console output.	Line Symbolic
Remove once hit	Select to remove the breakpoint from your project right after it has been hit.	Line Symbolic JavaScript Exception
Disable until breakpoint is hit	Select the breakpoint that will trigger the current breakpoint. Until that breakpoint is hit, the current breakpoint will be disabled. You can also select if you wish to disable it again or leave it enabled once it has been hit.	All types
Uncaught only	Select to be notified when you've hit a breakpoint on an uncaught exception.	JavaScript Exception breakpoints
When thrown	Select to suspend the program when you've hit a breakpoint on a caught exception: Any: on any exception. Objective-C only: only on exceptions in Objective-C code.	Exception
When caught	Select to suspend the program when an exception is caught.	Exception

Breakpoint statuses

Breakpoints can have the following statuses:

Status	Description
Verified	After you have started a debugger session, the debugger checks whether it is technically possible to suspend the program at the breakpoint. If yes, the debugger marks the breakpoint as verified.
Warning	If it is technically possible to suspend the program at the breakpoint, however there are issues related to it, the debugger gives you a warning. This may happen, for example, when it is impossible to suspend the program at one of the method's implementations.
Invalid	If it is technically impossible to suspend the program at the breakpoint, the debugger marks it as invalid. The most common cause for this is that there is no executable code on the line.
Inactive/dependent	A breakpoint is marked as inactive/dependent when it is configured to be disabled until another breakpoint is hit, and this has not happened yet.
Muted	All breakpoints are temporarily inactive because they have been muted.
Disabled	This breakpoint is temporarily inactive because it has been disabled.
Non-suspending	The suspend policy is set for this breakpoint so that it does not suspend the execution when hit.

Breakpoint icons

Depending on their type and status, breakpoints are marked with the following icons:

	Line	Symbolic	Exception
Regular
Disabled
Verified
Muted
Inactive/dependent
Muted disabled
Non-suspending
Verified non-suspending
Invalid

Productivity tips

Use breakpoints for debug printing: Use non-suspending logging breakpoints (sometimes referred to as watchpoints in other debuggers) instead of inserting print statements in your code. This provides a more flexible and centralized way of handling debug log messages.
Set logging breakpoints more quickly: To set a non-suspending logging breakpoint, hold Shift and click the gutter. This will not suspend the program execution and instead log a message like Breakpoint reached: MyClass.swift:36. If you want to log some expression that is in front of you in the editor, select it before holding Shift and clicking the gutter.
Add breakpoint descriptions: If you have many breakpoints in your project, you can add descriptions to breakpoints for ease of search. To do this, right-click a breakpoint in the Breakpoints dialog ⌃ ⇧ F8 and select Edit description from the menu. Now when you start typing the breakpoint name, it gets the focus.
Group breakpoints: You can organize breakpoints into groups, for example, if you need to mark out breakpoints for a specific problem. To do this, in the Breakpoints dialog ⌃ ⇧ F8, select a breakpoint you want to place in a group and select Move to group from the menu.
Test your program for concurrency issues: A good way to find out if a multi-threaded program is robust in terms of concurrency is to use breakpoints that only suspend one thread when hit. Stopping a single thread may reveal problems in the design of the application, which would not otherwise be evident.

Last modified: 26 August 2021