deploy: 4155e2938f

examples/basic_json_document__erase.cpp

@@ -0,0 +1,38 @@
+#include <iostream>
+#include <nlohmann/json_view.hpp>
+
+using json = nlohmann::json;
+using json_editable_document = nlohmann::json_editable_document;
+using json_editable_view = nlohmann::json_editable_view;
+
+int main()
+{
+    // a deprecated field is dropped from a configuration file, and a
+    // decommissioned replica is removed from the list -- "price" keeps its
+    // trailing zero, and the fields around the removed ones keep their order
+    const std::string text = R"({
+  "name": "cache",
+  "legacy_host": "db0",
+  "host": "db1",
+  "price": 19.90,
+  "replicas": ["db2", "db3", "db4"]
+})";
+
+    json_editable_document doc = json_editable_document::parse(text);
+
+    doc.erase(doc.root(), "legacy_host");                                      // (1) an object member
+    doc.erase(doc.root()["replicas"], 1);                                      // (2) an array element ("db3")
+    const std::size_t removed = doc.erase(json::json_pointer("/replicas/0"));  // (3) via a JSON pointer
+
+    std::cout << removed << '\n';
+    std::cout << doc.root().dump(2, ' ', false, json_editable_view::number_format::source) << "\n\n";
+
+    // the same edits on a plain json value: object_t is a std::map, so
+    // parsing already sorted the keys, and dump() rewrites every number to
+    // its shortest form, even "price", which was never touched
+    json plain = json::parse(text);
+    plain.erase("legacy_host");
+    plain["replicas"].erase(1);
+    plain["replicas"].erase(0);
+    std::cout << plain.dump(2) << '\n';
+}