tomevault-io Map Nil Safety
Problem
Reading from nil map returns zero value. Writing to nil map panics.
Pattern
WRONG - Write to nil map
var m map[string]int // nil map
m["key"] = 42 // PANIC: assignment to entry in nil map
CORRECT - Initialize with make
m := make(map[string]int)
m["key"] = 42 // OK
Reading is Safe
var m map[string]int // nil map
v := m["key"] // OK, v = 0 (zero value)
v, ok := m["key"] // OK, v = 0, ok = false
Quick Fix
- Always initialize maps with make() before writing
- Check if map is nil before range/write
- Reading from nil map is safe but returns zero values
Defensive Pattern
if m == nil {
m = make(map[string]int)
}
m["key"] = 42
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