Explore whether var in go can initialize the structure

This article is introduced by the go language tutorial column to introduce to you the issue of whether var can initialize the structure in golang. I hope it will be helpful to friends in need!

Background

The previous small article simply used goland to build the simplest golang demo. It has no practical value and uses golang syntax. There are also relatively few. In this section, we complete a simple crud operation, quickly understand some common operations of golang, and be able to master the basic grammar of golang

Learn the grammar in advance

• Convert string to int Use strconv.Atoi method in golang
  

• The return value of the method in golang can have multiple values, which is different from java, for example In the method of map[id], the first return value is value, and the second return value is bool type, indicating whether it exists.

• is more similar to the json serialization method in java , deserialization is the json.Unmarshal method, the first parameter is a byte array, the second parameter is the "address" of the serialized object, needs to add an &, the serialization method is json.Marshal Method, pay attention to the byte array returned by this method

The syntax used in the above section is often used in the following exercises, friends can simply memorize it

Exercise

1. We simply define a User class and use golang to complete the addition, deletion, and modification of this structure instance. We define a structure as shown below, with three Attributes Id, Name, Age

2. Because the addition, deletion, modification and query are done in the memory and no database is used, we need to define a global variable like java. , as a container to save data, as shown in the source code below, we use the keyword var to define a global variable map and initialize a record

3. Then define four "RequestMapping" is as follows

3.1 The main logic of the getUser method is to obtain the passed parameter id, and then obtain the user's basic information from the global variable based on the id

3.2 saveUser We process POST requests. Now in development, we generally parse the json data passed over to the corresponding one, and then save it to our global variables

3.3 updateUser is similar to saveUpdate. For the sake of simplicity, we only determine if the corresponding id in the global map exists, and then change the user object corresponding to this id, without comparing and replacing attributes.

3.4 deleteUser is even simpler, just delete the corresponding id in the map

Test

1.getUser’s test

2.saveUser’s test

3.UpdateUser test

##4.

Summary

This section mainly completes the addition, deletion, modification and search in the memory. In fact, if you fully master the basic syntax of golang, you will definitely feel that it is childish, but it does not matter. , some new students must have gained something. If you look at the above code carefully, you will definitely find some problems. You will find that there are only two ways for us to parse parameters, one is localhost:9090/user?id=1 This way of getting the id is to get the json in the post request. If we imagine @requestMapping(value="/user/{name}/ in spring mvc, it is localhost:9090/user?id=1 to get the id. The way to get it is to get the json in the post request. If we want to do this like @requestMapping(value="/user/{name}/{id}") in spring mvc, it won't work, and then get it through the @pathvariable method. Parameters, this is very useful in our daily work, but unfortunately, golang does not natively support such relatively complex parameter binding work. We will solve this problem through a data structure Trie

Source code address

https://github.com/BazingaLyn/jarvis

If you like this series of introductory tutorials, I hope you can follow it, like it and collect it, and the quality will be tripled Thank you~

Easter Egg

If you type the code by hand, you will find that (writer http.ResponseWriter, request *http.Request) needs to be written many times, goland A method to quickly generate shortcut keys is provided, but everyone's shortcut key settings may be different, but you can use the following method to quickly generate a method

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