Demystifying C: A Clear and Simple Path for New Programmers

Lazy loading only queries when accessing associations can easily lead to N 1 problems, which is suitable for scenarios where the associated data is not determined whether it is needed; 2. Emergency loading uses with() to load associated data in advance to avoid N 1 queries, which is suitable for batch processing scenarios; 3. Emergency loading should be used to optimize performance, and N 1 problems can be detected through tools such as LaravelDebugbar, and the $with attribute of the model is carefully used to avoid unnecessary performance overhead.

Laravel supports the use of native SQL queries, but parameter binding should be preferred to ensure safety; 1. Use DB::select() to execute SELECT queries with parameter binding to prevent SQL injection; 2. Use DB::update() to perform UPDATE operations and return the number of rows affected; 3. Use DB::insert() to insert data; 4. Use DB::delete() to delete data; 5. Use DB::statement() to execute SQL statements without result sets such as CREATE, ALTER, etc.; 6. It is recommended to use whereRaw, selectRaw and other methods in QueryBuilder to combine native expressions to improve security

Go generics are supported since 1.18 and are used to write generic code for type-safe. 1. The generic function PrintSlice[Tany](s[]T) can print slices of any type, such as []int or []string. 2. Through type constraint Number limits T to numeric types such as int and float, Sum[TNumber](slice[]T)T safe summation is realized. 3. The generic structure typeBox[Tany]struct{ValueT} can encapsulate any type value and be used with the NewBox[Tany](vT)*Box[T] constructor. 4. Add Set(vT) and Get()T methods to Box[T] without

JWT is an open standard for safe transmission of information. In Java, authentication and authorization can be achieved through the JJWT library. 1. Add JJWT API, Impl and Jackson dependencies; 2. Create JwtUtil tool class to generate, parse and verify tokens; 3. Write JwtFilter intercepts requests and verify BearerTokens in Authorization header; 4. Register Filter in SpringBoot to protect the specified path; 5. Provide a login interface to return JWT after verifying the user; 6. The protected interface obtains user identity and roles through parsing the token for access control, and ultimately realizes a stateless and extensible security mechanism, suitable for distributed systems.

json.loads() is used to parse JSON strings into Python data structures. 1. The input must be a string wrapped in double quotes and the boolean value is true/false; 2. Supports automatic conversion of null→None, object→dict, array→list, etc.; 3. It is often used to process JSON strings returned by API. For example, response_string can be directly accessed after parsing by json.loads(). When using it, you must ensure that the JSON format is correct, otherwise an exception will be thrown.

Use datetime.strptime() to convert date strings into datetime object. 1. Basic usage: parse "2023-10-05" as datetime object through "%Y-%m-%d"; 2. Supports multiple formats such as "%m/%d/%Y" to parse American dates, "%d/%m/%Y" to parse British dates, "%b%d,%Y%I:%M%p" to parse time with AM/PM; 3. Use dateutil.parser.parse() to automatically infer unknown formats; 4. Use .d

Python's ternary operator is used to concisely implement if-else judgment, and its syntax is "value_if_trueif conditionelsevalue_if_false"; 1. It can be used for simple assignment, such as returning the corresponding string based on positive and negative values; 2. It can avoid division errors, such as determining that the denominator is non-zero and then division; 3. It can select content according to conditions in string format; 4. It can assign labels to different elements in list derivation formula; it should be noted that this operator is only suitable for binary branches and should not be nested multiple layers. Complex logic should use the traditional if-elif-else structure to ensure readability.

Yes, a common CSS drop-down menu can be implemented through pure HTML and CSS without JavaScript. 1. Use nested ul and li to build a menu structure; 2. Use the:hover pseudo-class to control the display and hiding of pull-down content; 3. Set position:relative for parent li, and the submenu is positioned using position:absolute; 4. The submenu defaults to display:none, which becomes display:block when hovered; 5. Multi-level pull-down can be achieved through nesting, combined with transition, and add fade-in animations, and adapted to mobile terminals with media queries. The entire solution is simple and does not require JavaScript support, which is suitable for large