When developing templates for AnQiCMS, we often encounter such questions: The background data is a Go language slice (Slice) or map (Map) structure. If you want to output these data in a readable JSON string format in the front-end template, the built-in of AnQiCMS comes withstringformatCan the filter do the job? This is indeed a very practical need, after all, JSON format is ubiquitous in modern web development.

First, let's delve into it deeper.stringformatFilter. According to the AnQiCMS template tag document,stringformatthe filter is described as 'Can format numbers and strings into the specified format for output. Equivalent tofmt.Sprintf()This means it inherits the powerful functions and flexibility of the Go language standard library.fmt.SprintfFunctions, allowing us to use Go-style formatting verbs (such as%d/%s/%.2fFormat output content finely using （）.

For example, if we have a number that needs to be kept with two decimal places, we can use{{ value|stringformat:"%.2f" }}; or if a string needs to be embedded into a text block,{{ "你好"|stringformat:"Chinese: %s" }}This can be put to good use. This indicatesstringformatIt is very efficient and intuitive when dealing with basic data types (such as integers, floating-point numbers, and ordinary strings).

However, when it comes to complex data types such as slices (Slice) and maps (Map) in the Go language, the situation is different. When we usefmt.Sprintffunction (and the correspondingstringformatfilter) when formatting a Go slice or map, for example using%v(default format) or%sIt will not automatically convert it to a standard JSON string. Instead, it will output the 'native string representation' of these data types in Go language.

For example, a Go languagemap[string]interface{}type, if output directlystringformat:"%v"You might see something likemap[key1:value1 key2:value2]this form. And a[]stringslice of a type might be displayed as[element1 element2].These outputs contain data content, but they do not comply with the strict syntax rules of JSON: for example, keys and string values must be enclosed in double quotes, elements must be separated by commas, and the entire structure must be correctly nested with square brackets (for arrays) or curly braces (for objects).

Therefore, the direct answer is:Anqi CMS'sstringformatThe filter itself cannot convert Go language slices or Maps into the 'readable JSON string format output' we usually refer toIt's design goal is to follow the Go programming language.fmt.SprintfNormalize the format universally, rather than specializing in JSON serialization.JSON serialization is a more specific task that requires adherence to a strict set of specifications to ensure the output format is valid JSON.

If we indeed have a strong need to output complex data structures as JSON strings in the template, we may need to adjust our strategy. The most direct and recommended method is to pass the slice or Map data through the Go standard library'sencoding/jsonSerialize the package, convert it into a well-formatted JSON string, and then pass this JSON string as a variable to the template.The template can directly output this JSON string after receiving it.safeFilter to avoid unnecessary escaping of characters such as quotes by the template engine.

In general,stringformatThe filter is a very useful tool in the AnQiCMS template engine, providing us with powerful string and basic data type formatting capabilities.But when it comes to specific tasks like converting complex Go data structures to standard JSON strings, it is not the preferred choice, and we need to combine the background data processing logic more flexibly to complete it.

Common Questions (FAQ)

  1. Question: If I have already serialized the data into a JSON string in the background, how can I safely output it in the template?Answer: If you have already converted a slice or Map into a complete JSON string in your Go language logic background (for examplejsonString := json.Marshal(myGoData)Pass the value to the template, and then you can use it directly in the template{{ jsonString }}Output. But to ensure that special characters (such as double quotes) in the JSON string are not misinterpreted or escaped by the template engine, it is recommended to usesafea filter, that is{{ jsonString|safe }}.

  2. Question: Is there a way to view the original structure of a Go slice or map in an AnQiCMS template without formatting?Answer: AnQiCMS's template engine providesdumpfilters that can be used to print the structure type and value of variables. For example,{{ mySliceOrMap|dump }}It will output the detailed Go language representation of the Go slice or Map in memory, including its type and content.Although this is not in JSON format, it is very helpful for debugging and understanding the representation of data structures in templates.

  3. Why does AnQiCMS not provide a template filter similar tojson_encode?Answer: This is usually due to design philosophy and performance considerations.The primary responsibility of the template engine is to display data, rather than handle complex business logic or data transformation.The JSON encoding often involves more complex error handling and data structure validation, which is more suitable to be completed in the background logic of the Go language.Convert data processing to the background can ensure data accuracy, reduce overhead during template rendering, and maintain the 'lightweight' nature and focus on display of the template.encoding/jsonThe library is already very mature and efficient.