在golang中不同位置初始化地图的不同值

Question

I'm creating a map of structs to hold different information. A sample struct I am using is:

type Test struct{
  Value1 string
  Value2 string
  Value3 string
  Value4 string
}

func main() {
  testMap := make(map[string]*Test) //using a pointer to map
  func2(testMap)
  //pass map to another function for more additions.
}

func func2 (testMap map[string]*Test) {
  a, b := getVal(); //get some random values
  res := concat(a,b) //basically create a string key based on values a and b
  testMap[res].value1 = a   //****
  testMap[res].value2 = b
  //do something else
  testMap[res].value3 = "hello"

}

I'm basically trying to create a map and add values to it as I get them, but im getting a invalid memory address or nil pointer dereference error on **** line (see code for ***).

Answer 1

Try:

func func2 (testMap map[string]*Test) {
  a, b := getVal(); //get some random values
  res := concat(a,b) //basically create a string key based on values a and b
  testMap[res] = &Test{
     Value1: a,
     Value2: b,
     Value3: "string",
  }

}

Or if you want to create the object first, then populate the value, try

func func2 (testMap map[string]*Test) {
  a, b := getVal(); //get some random values
  res := concat(a,b) //basically create a string key based on values a and b
  testMap[res] = &Test{}
  testMap[res].value1 = a   //****
  testMap[res].value2 = b
  //do something else
  testMap[res].value3 = "hello"

}