Use pointer fields when a partial-update endpoint needs to distinguish a supplied value—including false, 0, or ""—from an omitted field. But a pointer alone does not reliably distinguish an omitted JSON member from one explicitly set to null. If those states have different meanings, track presence separately or choose a patch format that expresses the needed operation.
Define what omission, null, and a value mean
Choose the API contract before choosing the Go type. For each field, decide whether omission means “leave unchanged,” whether null means “clear” or “reject,” and whether a concrete zero value is a valid update.
| JSON request state | Common meaning in a partial update | Information the server must retain |
|---|---|---|
| Member absent | Leave the stored value unchanged | Whether the member was present |
Member present with null |
Clear or remove the value, or reject the request | Presence and nullness |
| Member present with a value | Set the value, including "", 0, or false |
Presence and the concrete value |
The distinction matters beyond decoding: validation and persistence must preserve the same intended action. A request DTO designed for partial updates is often safer than reusing a domain or persistence struct whose fields do not encode those actions.
When pointer fields are enough
A pointer field such as Name *string is compact and useful when the endpoint only needs to tell “no concrete value supplied” from “a concrete value supplied.” A non-nil pointer can represent an explicit empty string, while a nil pointer avoids interpreting an omitted false, 0, or empty string as an update.
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- Read Before You Buy — No Video Output: These adapters support charging and USB 2.0 data transfer, but cannot transmit video signals. Except for standard USB webcams (which use USB data only), they are not compatible with HDMI/DisplayPort cables, video-capable USB-C hubs, or docking stations with video output.
- Convert USB-A Ports to USB-C: Designed to connect USB-C earphones, cables, flash drives, card readers, and other USB-C accessories to standard USB-A ports. Plug-and-play with no drivers or software required.
- Aluminum Alloy Housing: Built with a sturdy aluminum alloy shell that aids in heat dissipation and protects against daily wear and scratches. Designed to maintain a stable and secure connection.
- Compact & Travel-Friendly: The ultra-compact design allows the adapter to stay plugged into your device without blocking adjacent ports or adding bulk, reducing wear and tear on your original USB ports.
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However, ordinary pointer decoding does not provide a dependable three-state record of omitted, explicit null, and concrete value. If omission means “keep the existing value” but null means “clear it,” a pointer’s nil state is insufficient to choose between those actions.
When to track presence separately
If omitted, null, and concrete value each have distinct meanings, use a representation that retains both member presence and nullability. One conceptual wrapper can contain Set bool, Null bool, and Value T. Its decoder must mark the field set when the JSON member occurs, then distinguish null from a decoded value.
Rank #2
- 5-in-1 USB-C Hub: Experience comprehensive connectivity featuring a Power Delivery input, two USB-A 2.0 ports, a USB-A 3.0 port, and an HDMI port. (Note: The USB-C power delivery input port is only for connecting an external wall charger to power your laptop and cannot power peripheral devices.)
- 90W Pass-Through Charging: Achieve optimal charging with 90W pass-through power to your laptop, supported by a total input of 100W, with the hub reserving 10W for operational efficiency. (Note: Wall charger not included.)
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- What You Get: Anker USB-C Hub (5-in-1, 4K HDMI), welcome guide, 18-month warranty, and our friendly customer service.
This is a design sketch, not drop-in implementation code. Define and test behavior for omitted members, explicit null, malformed input, repeated decoding into a reused value, nested objects, validation, and output marshaling. A nullable type that does not also track input presence can still lose the distinction between “leave unchanged” and “set null.”
What JSON encoding options do—and do not do
omitempty concerns encoding a Go value back to JSON; it does not record whether an incoming object contained a member. The Go encoding/json documentation describes empty values to include false, zero, nil pointers and interfaces, and empty arrays, slices, maps, and strings. The omitzero option omits a Go zero value and supports an IsZero method; it likewise does not solve decoder-side presence tracking. See the Go encoding/json documentation.
Rank #3
- Sleek 7-in-1 USB-C Hub: Features an HDMI port, two USB-A 3.0 ports, and a USB-C data port, each providing 5Gbps transfer speeds. It also includes a USB-C PD input port for charging up to 100W and dual SD and TF card slots, all in a compact design.
- Flawless 4K@60Hz Video with HDMI: Delivers exceptional clarity and smoothness with its 4K@60Hz HDMI port, making it ideal for high-definition presentations and entertainment. (Note: Only the HDMI port supports video projection; the USB-C port is for data transfer only.)
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For the versioned v2 package, the encoding/json/v2 documentation explicitly says omitempty has no effect when unmarshaling. Treat these as package and version-specific implementation details, and check the documentation for the Go version and JSON package your project uses.
When a patch format is a better fit
JSON Merge Patch
RFC 7396 defines JSON Merge Patch: an omitted object member leaves the target member untouched, while a member set to null removes it. The format uses the media type application/merge-patch+json. It fits object updates where null means removal, but not a model that must represent an explicit stored null as an ordinary value. The RFC authors James M. Snell and Paul Hoffman state: “This design means that merge patch documents are suitable for describing modifications to JSON documents that primarily use objects for their structure and do not make use of explicit null values.”
Rank #4
- Dual Converters, Infinite Potential：Includes 2× USB C male to USB A female adapters and 2× USB A male to USB C female adapters. Perfect for a wide range of uses—tablets with Bluetooth keyboards, expand USB ports on macbook, and more. Two different converters for all your daily needs
- Next-Level 10Gbps & 3A Charging: No more slow 480Mbps, this usb to usb c adapter has a transfer speed of up to 10Gbps, allowing you to do more transferring in less time. This usb adapter fits both USB A and USB C charger, supporting up to 3A fast charging
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- Broad Compatible: The usb c to usb adapter widely supports all USB C/ USB A devices like laptops, tablets, cellphones, car chargers, and phone chargers. Such as compatible with MacBook Pro/Air 2023/2022, Thunderbolt 4/3 Devices,Apple MagSafe Watch 9/8/7/SE/Ultra, iPad Pro 2022/2021, Samsung Galaxy S23/S20/S10, and iPhone 17/16/15 Pro. Plug and play
- Please Note: To reach 10Gbps speed, keep the cable under 3.3 ft. For USB A Male to USB C adapters, try flipping the USB C connector. USB C Male to USB A adapters support bidirectional 10Gbps transfer within 3.3 ft
JSON Patch
RFC 6902 defines JSON Patch as a sequence of operation objects, using the media type application/json-patch+json. Operations include add, remove, replace, move, copy, and test. This format makes actions explicit, but the server must parse, validate, and apply the operations. A failed operation means the entire patch document is not deemed successful, consistent with HTTP PATCH atomicity.
Choose by semantics, not syntax
- Use pointer fields for a straightforward optional request field when omission means “keep the current value” and null does not need a separate meaning.
- Use a presence-aware nullable wrapper or preserve raw member presence when omitted, null, and a concrete value mean different things.
- Use JSON Merge Patch when object-merge behavior suits the resource and null should remove a member.
- Use JSON Patch when clients need an explicit operation list and the server can validate and apply it.
Before implementation, document the behavior for zero and empty values, invalid types, unknown fields, nested objects, arrays, nullability, and persistence. The patch format is part of the API contract, so changing its meaning later can break clients.
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Best Value
- 5-in-1 Connectivity: Equipped with a 4K HDMI port, a 5 Gbps USB-C data port, two 5 Gbps USB-A ports, and a USB C 100W PD-IN port. Note: The USB C 100W PD-IN port supports only charging and does not support data transfer devices such as headphones or speakers.
- Powerful Pass-Through Charging: Supports up to 85W pass-through charging so you can power up your laptop while you use the hub. Note: Pass-through charging requires a charger (not included). Note: To achieve full power for iPad, we recommend using a 45W wall charger.
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