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54 lines
1.7 KiB
Markdown
54 lines
1.7 KiB
Markdown
---
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title: "S03. Use Path Parameters"
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order: 22
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status: "draft"
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---
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For dynamic URLs like `/users/:id` — the staple of REST APIs — just put `:name` in the path pattern. The matched values end up in `req.path_params`.
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## Basic usage
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```cpp
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svr.Get("/users/:id", [](const httplib::Request &req, httplib::Response &res) {
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auto id = req.path_params.at("id");
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res.set_content("user id: " + id, "text/plain");
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});
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```
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A request to `/users/42` fills `req.path_params["id"]` with `"42"`. `path_params` is a `std::unordered_map<std::string, std::string>`, so use `at()` to read it.
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## Multiple parameters
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You can have as many as you need.
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```cpp
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svr.Get("/orgs/:org/repos/:repo", [](const httplib::Request &req, httplib::Response &res) {
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auto org = req.path_params.at("org");
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auto repo = req.path_params.at("repo");
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res.set_content(org + "/" + repo, "text/plain");
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});
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```
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This matches paths like `/orgs/anthropic/repos/cpp-httplib`.
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## Regex patterns
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For more flexible matching, use a `std::regex`-based pattern.
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```cpp
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svr.Get(R"(/users/(\d+))", [](const httplib::Request &req, httplib::Response &res) {
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auto id = req.matches[1];
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res.set_content("user id: " + std::string(id), "text/plain");
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});
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```
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Parentheses in the pattern become captures in `req.matches`. `req.matches[0]` is the full match; `req.matches[1]` onward are the captures.
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## Which to use
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- For plain IDs or slugs, `:name` is enough — readable, and the shape is obvious
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- Use regex when you want to constrain the URL to, say, numbers only or a UUID format
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- Mixing both can get confusing — stick with one style per project
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> **Note:** Path parameters come in as strings. If you need an integer, convert with `std::stoi()` and don't forget to handle conversion errors.
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