如何分配给嵌套地图

Question

我有类似的东西type rateLimit struct {    Count    int}type RateLimiter struct {    cachePeriod   time.Duration    rateLimits map[string]*rateLimit}和这样的功能：func NewRateLimiter(////) *RateLimiter {    rateLimits := make(map[string]*rateLimit)    return &RateLimiter{        cachePeriod:   cachePeriod,        rateLimits: rateLimits,    }}此结构允许您创建嵌套结构，例如 rateLimits["foo"] = a但我正在尝试进行更改以使其嵌套并且我可以做到rateLimits["foo"]["bar"] = a我尝试将结构更改为 rateLimits := make(map[string]map[string]*rateLimit)和type rateLimiter struct {    cachePeriod   time.Duration    rateLimits map[string]map[string]*rateLimit}但我得到panic: assignment to entry in nil map [recovered] panic: assignment to entry in nil map

Answer 1

rateLimits := make(map[string]map[string]*rateLimit)

rateLimits["foo"] = make(map[string]*rateLimit)

rateLimits["foo"]["bar"] = a

rateLimits := map[string]map[string]*rateLimit{"foo": {"bar": a}}

Answer 2

您必须制作嵌套地图：

func setNested(m1 map[string]map[string]string, k1, k2 string, v string) {

    m2 := m1[k1] 

    if m2 == nil {

       m2 = make(map[string]string)

       m1[k1] = m2

    }

    m2[k2] = v

}

像这样使用它：

 setNested(rateLimits, "foo", "bar", a)