At 24:56 in "Bring Core Data concurrency to Swift and SwiftUI" there's the following discussion: But here's the important part. Changes to the request are committed whenever the results getter is called, so to update both the sorting and the sectioning safely... I need to update the configuration on a reference to the results that I've pulled into a local. The code in question is a property: @SectionedFetchRequest( sectionIdentifier: \.day, sortDescriptors: [SortDescriptor(\Quake.time, order: .reverse)]) private var quakes: SectionedFetchResults<String, Quake> And it is updated with: .onChange(of: selectedSort) { _ in let sortBy = sorts[selectedSort.index] let config = quakes config.sectionIdentifier = sortBy.section config.sortDescriptors = sortBy.descriptors } It's unclear what the value/reference semantics here are. quakes looks like a value type, but this is clearly treating it as a reference type. But if it's a reference type, why is the config local variable important? It feels like some kind of magic is happening here. Why is this local variable necessary, and how would I know this?

I have a custom Instrument with a os-signpost-interval-schema that captures a "state" string. I would like the final plot value to be <state>: <duration>, but I don't know how to get the duration into the string. My working schema is the following, which just stores the state itself in the column: <os-signpost-interval-schema> <id>state-interval</id> <title>State Interval</title> <subsystem>"..."</subsystem> <category>"..."</category> <name>"state"</name> <start-pattern> <message>?state</message> </start-pattern> <column> <mnemonic>state</mnemonic> <title>State</title> <type>string</type> <expression>?state</expression> </column> </os-signpost-interval-schema> I would like to change the expression in the column to (str-cat ?state ": " ?duration), but that fails with: Variable '?duration' must appear in a pattern element to be used in a later expression. I don't see any way to compute this later in the graph, lane, or plot. I've also tried explicitly creating a <duration-column>, but that doesn't seem to change anything. The rest of the pieces include the table: <create-table> <id>state-table</id> <schema-ref>state-interval</schema-ref> </create-table> And the lane, which I would like to display as <state>: <duration> rather than just the duration: <lane> <title>State</title> <table-ref>state-table</table-ref> <plot> <value-from>state</value-from> </plot> </lane>

I have a custom Instrument that is generally paired with Apple's HTTP Traffic instrument. Combining them in a template is inconvenient because there is no way to automatically filter to just the URLSession I want. The user must drill down into a long list of sessions and servers every time the instrument is run. The layout is also awkward because my Instrument's output is a long way from the specific HTTP track I want. Pinning these specific tracks is good, but has to be done every time and cannot be saved as a template. I would like to extract the relevant information directly into my custom instrument, so just the information I want is visible, and in an order that is useful. I can import the data from HTTPTracing and build my own tables, but is there a way to import the plot itself and reuse it? I would rather not have to re-implement Apple's fairly complex plot. If not, is there a way to access Apple's code for the HTTPTracing plots so that I can add it in my own instrument?